EU nations must step up their military co-operation as they cannot simply rely on the US to defend them, EU Commission President Jean-Claude Juncker says.

"Our deference to Nato can no longer be used as a convenient alibi to argue against greater European efforts.
"We have no other choice than to defend our own interests in the Middle East, in climate change, in our trade agreements," he said in Prague.
US President Donald Trump has urged Nato allies to boost defence spending.
Last month German Chancellor Angela Merkel said Europe could no longer "completely depend" on the US and UK, following the election of President Trump and the triggering of Brexit.
The UK and France are by far the strongest military powers in the EU, so UK withdrawal potentially weakens Europe's collective military muscle.
Only five of Nato's 29 member states - the UK, US, Poland, Greece and Estonia - have met Nato's target for each member to spend at least 2% of their GDP (national output) on defence.
Mr Juncker told the Prague defence and security conference on Friday that "the way forward starts with making sure that we spend what is needed on our defence".
Cold War-era tensions have resurfaced since Russia annexed Crimea in 2014 and pro-Russian rebels carved out a separatist region in eastern Ukraine.
"The protection of Europe can no longer be outsourced," Mr Juncker said.
But he stressed that "competition between the EU and Nato is not an option".
He praised the EU-Nato partnership in some key hotspots around the world: Afghanistan, the Balkans and the Horn of Africa.
But he deplored inefficiencies in European military spending and planning, saying much more co-operation on defence projects was needed in the EU.
Mr Juncker said the EU was spending on average €27,000 (£24,000; $30,000) per soldier on equipment and research, whereas the US was spending €108,000.
"Together, we spend half as much as the United States, but even then we only achieve 15% of their efficiency," he said.
"Absurdly, there are more helicopter types than there are governments to buy them! We must do better."
The UK has long been one of the strongest voices in the EU against any moves towards forming a European army. The UK says the EU must not duplicate Nato's role as the main pillar of European defence.
However, Mr Trump's criticisms of Nato have raised questions about the US commitment to defending Europe.
On Wednesday the European Commission announced the launch of a European Defence Fund, agreed with national governments, to help finance joint military projects.
The EU will earmark budget funds to co-finance projects that EU member states want to develop together.
Under the plan, €500m will be made available annually after 2020 for joint military research, and another €1bn annually for joint investment and purchases of military equipment, such as drones and helicopters.
The EU has formed some joint battlegroups, intended as a rapid reaction force, but they have never been tested in combat.


Criminals could steal large amounts of money from people's pockets using a mobile phone, because of a glitch in Visa's contactless credit cards, researchers have said.

A study at Newcastle University found the flaw applied to foreign currency transactions.
But the scientists acknowledged they had not examined the security checks banks have in place.
Visa said it would be "very difficult" to carry out such a theft in reality.
Transactions using contactless credit cards do not use a Pin code, so have a Â£20 limit as a safeguard.
But the study found a transfer of anything less than a million units in any foreign currency would be approved.
Researchers set up a "point of sale terminal" - the equivalent of a card reader in a shop - using a mobile phone.
They said transactions with the card were approved in less than a second.
"All the checks are carried out on the card rather than the terminal, so at the point of transaction there is nothing to raise suspicions," said Martin Emms, lead researcher on the project.
"By pre-setting the amount you want to transfer, you can bump your mobile against someone's pocket or swipe your phone over a wallet left on a table and approve a transaction."
He acknowledged the study had not looked at the security systems banks have in place to prevent fraud.
But he added it was not clear, looking at the payment protocol, how banks would deal with the problem.
Visa said it had reviewed the research and it did not take into account "multiple safeguards put into place throughout the Visa system".
"For these reasons we do not believe the findings to be a cause for concern, as it would be very difficult to complete a fraudulent payment of this kind outside a laboratory environment," its statement said.


The organisation behind the PISA international school rankings has said Wales should continue its radical reform of the curriculum.

The  Organisation for Economic Co-operation and Development (OECD) was asked by Education Secretary Kirsty Williams to report on changes.
It published its findings on the biggest overhaul since 1988 on Tuesday.
Literacy, numeracy and digital competency form the core of the new curriculum, set to be in place by 2021.
In December, the OECD published the PISA results, with Wales coming bottom of the four home nations and below countries including Singapore, Vietnam and Slovenia.
A new central curriculum has now been outlined, that gives schools the freedom to teach around it with areas such as the humanities, language, health and wellbeing.
The current four key stages of education will be replaced with "progression steps" at the ages of five, eight, 11, 14 and 16.
More than 150 pioneer schools are beginning to pilot the new way of learning.
The OECD said the changes should be underpinned by sustained investments.
But it warned the Welsh Government against trying to implement additional education policies, noting there is a risk of the reform journey becoming piecemeal and not reaching its objectives
Ms Williams said: "We are already taking action on many of their recommendations, from creating a new national academy for leadership, transforming initial teacher education, launching new professional standards, and introducing a national approach to professional learning.
"Our job is to continue our national mission of education reform focused on driving up standards and helping every learner in Wales, whatever their background, fulfil their potential."
The 61-page report, published on Tuesday morning to a conference of head teachers in Cardiff, notes there are still concerns about the quality of teaching.
But the OECD said it hopes the new curriculum under development will "significantly raise the bar" in terms of what Wales expects of its teachers.
It said: "In the future Wales will need a different type of teaching professional; one who has significantly more responsibility and one who understands the 'why' and the 'how' of teaching as well as the 'what'.
"These aspirations have major implications for both initial teacher training and for continuous professional learning."
The OECD also called on the Welsh Government to speed up development of leadership standards with the success of the new curriculum dependent on having "sufficient numbers" in schools.
National Union of Teachers Cymru's general secretary David Evans said in many cases the report outlines "age old arguments that everyone is very aware of" and committed to improving.
He added: "In part we can reflect on this as a consistent narrative that supports the direction unions have been setting and, at least in recent years, the Welsh Government have been more aligned with.
"At the same time it is somewhat depressing that once again these recommendations are problems that are outstanding."
Mr Evans also said there needed to be some "deep and honest thinking" from the Welsh Government about why "some of the same issues are being highlighted again.
The OECD's finding will not come as a surprise to the Education Secretary Kirsty Williams, after all she commissioned their report and her response is what is to be expected. Indeed many of the areas it highlights are already being tackled.
What is interesting is the stern warning from the OECD not to add yet more policies to the raft of measures which have been put in place since 2014.
How difficult is it for politicians simply to sit and wait to see if their policies come to fruition - especially if they face a clamour for change from parents and opposing political parties.
With just four years before a new and radical curriculum is due to be taught in the nation's schools, the clocking is ticking. The OECD says the Welsh Government's efforts to recruit highly qualified individuals must be matched with high quality initial teacher training.
It says progress has been slow, but transforming the profession to meet the demands of the new curriculum "also requires those who are already teaching to adapt to constantly changing demands and continuously develop their skills".
Leadership is another clearly an area of concern for the OECD. It recommends that the Welsh Government and local authorities should promote the use of business managers for schools or groups of schools to reduce the administrative burden on school leaders.
It found that school leaders especially at primary level are "often burdened by administrative tasks" which distracts them from improving the quality of teaching and learning. School leaders I speak to talk of the sometimes daily deluge of directives they face from local and national levels.


A previously unseen video of one of Britain's most infamous spies describing his career as a Soviet agent has been uncovered by the BBC.

The tape is of Kim Philby giving a secret lecture to the Stasi, the East German Intelligence Service, in 1981.
It is the first time the ex-MI6 officer can be seen talking about his life as a spy from his recruitment to his escape.
He describes his career rising up the ranks of MI6 whilst providing its secrets to the Soviet Union's KGB.
He ends with advice to the East German spies.
"Dear Comrades."
With those two words spoken in an impeccable upper-class English accent, one of Britain's most famous spies and its greatest traitor begins a masterclass in betrayal to a select audience of East German spies.
Philby's hour-long address was preserved on video tape and never seen in public until now.
The BBC unearthed it in the official archives of the Stasi in Berlin.
It was never made for public consumption (and the grainy video and poorly synchronised sound shows the limits of technology at the time), but that means the former MI6 officer is open about his career in a way never heard before.
After an introduction from East German spymaster Markus Wolf, who was so elusive to western spy agencies that he was known for many years as "the man without a face", Philby makes his way to the lectern to a hero's welcome.
"I must warn you that I am no public speaker," Philby says.
"I've spent most of my life trying to avoid publicity of any kind."
That much is true. Previously the best known video of Philby was him giving a 1955 press conference in his mother's London flat.
On that occasion he said very little, only denying he was a communist.
In this newly discovered video, for the first time, we hear Philby himself boast about what he calls his "30 years in the enemy camp".
He describes himself as born into "the ruling class of the British Empire" and explains how he first was drawn towards communism at Cambridge.
He details his recruitment by the Soviet intelligence service, later known as the KGB, after he returned from working with activists in Austria.
The most surprising thing about his recruitment, he says, was that it happened at all since he had no real job or prospects at that moment.
"It was essentially a long range project. No immediate results were expected or could have been expected."
He says his Soviet contact did express his ambitions for his recruit.
"It was made perfectly clear to me that the best target in the eyes of the Centre in Moscow would be the British Secret Service."
Philby details how he spent years trying to work his way in - turning to journalism, working for The Times newspaper, covering the Spanish Civil War, building up contacts in the establishment and then as war came dropping hints about his desire to work for government.
At last, he was interviewed and accepted in to the inner sanctum of the British state - the Secret Intelligence Service - SIS (or as it is popularly known MI6).
In one of the most remarkable sections of the talk, Philby then reveals just how easy it was to steal secrets from Britain's secret service.
He says that he simply made friends with the archivist who managed the files by going out two or three times a week for a drink with him.
This allowed Philby to get hold of files which had nothing to do with his own job.
"If there had been proper discipline in the handling of papers in SIS that would have been quite impossible.
"But there was, in fact, no discipline."
Philby goes on to explain what he did with all the documents.
"Every evening I left the office with a big briefcase full of reports that I had written myself, full of files and actual documents from the archive.
"I used to hand them to my Soviet contact in the evening.
"The next morning I would get the files back, the contents having been photographed and early the next morning I would put them back in their place. That I did regularly year in year out."
Philby, a Soviet agent, is then appointed number two in a new MI6 section, devoted to countering Soviet espionage.
His KGB handler next instructs him to get the top job by removing his boss, Felix Cowgill.
"I said 'Are you proposing to shoot him or something?'" Philby recalls asking.
Instead his instructions were to use bureaucratic intrigue.
"So I set about the business of removing my own chief. You oughtn't to listen to this," he tells the audience of secret service officers to considerable laughter.
He succeeded.
"It was a very dirty story - but after all our work does imply getting dirty hands from time to time but we do it for a cause that is not dirty in any way," Philby explains.
"I have to admit that was the most blatant intrigue against a man I rather liked and I admired but the instructions stood and nothing I could do would alter them."
There is one episode which is usually cited to illustrate the human cost of Philby's treachery.
When he was posted to Washington DC as MI6's liaison with the CIA and FBI, he betrayed an operation to secretly send thousands of Albanians back into their country to overthrow the communist regime.
Many were killed.
In his lecture, Philby tries to turn it to his credit - even claiming he helped prevent World War Three.
He claims that if he had not compromised the operation and it had succeeded, the CIA and MI6 would have tried it again in countries like Bulgaria.
He says the Soviet Union would then have become involved, leading to an all-out war.
While he was in Washington, two fellow Cambridge spies, Guy Burgess and Donald Maclean, fled to Moscow, leading to suspicions about Philby and his interrogation.
He says there were two reasons why he got away with his espionage for so long.
The first was the British class system, which could not accept one of their own was a traitor.
The second was the fact that so many in MI6 had so much to lose if he was proven to be a spy.
Philby did officially leave MI6 but remarkably was soon taken back.
He became an agent based in Beirut under cover of being a newspaper journalist. This allowed him to resume his spying.
Philby ends the formal section of his talk with an account of his escape from Beirut which he uses to mock MI6.
In 1963, an MI6 colleague came to confront him with new evidence pointing to his work for the Soviets.
Philby bluffed and stalled. Another MI6 officer was then left to watch over him.
But that man was an avid skier.
Philby says that news came in of a fresh snowfall and the officer could not resist heading off to the Lebanese mountains to make the most of it.
At that point, Philby got the signal from the KGB for his departure and was able to slip away.
Philby then sits down and takes questions from the East German spies.
A fascinating first answer explains how he first acquired his communist beliefs and was then able to hold on to them despite living in the West.
He praises his Soviet handler and advises his audience that they need to take care of the political as well as physical health of any agents they run.
Philby finishes with one piece of advice to the spies gathered before him that had served him well: never confess.
"If they confront you with a document with your own handwriting then it's a forgery - just deny everythingâ€¦
"They interrogated me to break my nerve and force me to confess.
"And all I had to do really was keep my nerve. So my advice to you is to tell all your agents that they are never to confess."
This video, designed to be secret, is a chance to see Philby giving his own account of his life as a spy.
The tone is one of total self-confidence.
Philby died in Moscow in 1988 just before the collapse of the Communist ideal which he had spent his life serving.
Hear "The Philby Tape" on BBC Radio 4 on Monday at 20:00 BST.


The release of Disney's Beauty and the Beast has been postponed in Malaysia.

The much-anticipated film sparked controversy last week after it emerged it would feature a "gay moment".
It was due for release in Malaysia on Thursday, but Disney said it was being held for a "review" of its content.
The Malaysian Censorship Board (LPF) said on Tuesday it had approved the screening but with "a minor edit concerning a gay moment in the film".
Homosexual activity is illegal in Muslim majority Malaysia, although the country's tourism minister has said banning the film is "ridiculous".
A new release date has yet to be announced.   The live-action remake was granted a "P13 parental guidance classification".
"We have approved the film so there is no more issue. Once a film receives approval, it means it can be screened," LPF Chairman Datuk Abdul Hamid said.
"However, the date of screening and where the screening takes place is not under LPF's jurisdiction. We only look at the content and give a decision on whether the movie gets approved or not."
Local cinema chains have been offering refunds for customers who have purchased tickets in advance.
Beauty and the Beast director Bill Condon has spoken about the "exclusively gay moment" in the film.
It involves LeFou - the sidekick of the film's main antagonist Gaston - who tries to come to terms with feelings for Gaston that swing between lust and admiration, as a side-plot to the main story.
The decision to review the Disney classic in Malaysia courted criticism from netizens, many of whom called it "stupid and laughable".
"Malaysia bans 'Beauty and the Beast' but is okay with nonsense Malay movies with no moral values, just full of brainless jokes," wrote a Twitter user in a tweet which drew more than 4,500 re-tweets.
Priyanka Laxmiâ€


Theo Walcott has improved so much this season, it is as if he has flicked a switch in his head.

You can see highlights of Arsenal v Middlesbrough on Match of the Day at 22:20 BST on Saturday on BBC One and the BBC Sport website.
Walcott now sees himself as a winger, not a striker, but his turnaround is not just because he is now focusing on succeeding in one position for Arsenal.
It is down to a change in his attitude and application, which has brought him a greater end product - he has already scored more Premier League and Champions League goals than he did in the whole of last season.
He has also increased his defensive work and has already made more tackles (14) in the league in 2016-17 than in the two previous campaigns combined (11).
It is like the Gunners only had half a player - until now.
Theo has a different mindset because at the age of 27 he has reached a stage of his career where alarm bells are ringing.
He has been at the club for more than 10 years now and he is not prepared to be a bit-part player any more.
Rather than being someone who comes in and out of the team, he wants to be a part of the main story at Arsenal.
It seems to be the case that he is now thinking: 'I have to be in the team and I am going to do everything possible to be there.'
That would have started on day one of pre-season, which is why Wenger spoke in the summer about seeing a different player - and that determination has not stopped since.
It was the same with his England performances after he suffered the disappointment of missing out on the squad for the European Championship finals.
He did not play as well against Malta and Slovenia as he has been performing for the Gunners, but he could not be accused of not applying himself in the right way.
I was at Arsenal and working with the backroom staff while I got my coaching badges when Walcott joined from Southampton aged 16 in January 2006.
The scout who found him for Saints, Malcolm Elias, knew I was working for the Gunners and asked me to help Theo bed in a little bit, which I gladly did.
I remember watching him very closely in all the passing drills and running exercises in training, and he looked very comfortable right from the start.
That is unusual because normally when a kid comes into the first-team picture at that age, he struggles to complete everything in a session.
They get out of breath, and they lose some of their smoothness because they are at their limits. Not Theo, though.
I have a feeling, looking back, that it was all a bit too easy for him and he did not have to push himself.
He had some extra gears he was not using - and we are seeing them now. His problem, until now, has been working out how to find them effectively.
When you ask for more from a fast, attacking player like Walcott, you do not want them to play in too much of a hectic fashion, or try things beyond what they are capable of.
In the past, I think that has happened and Theo has sometimes over-stretched himself when he has tried to go through the gears, which has affected his confidence.
This season, everything about his play is much more controlled and suggests he has got the mental side of things spot on.
That is why Wenger is saying he is playing with more freedom - it is all in his mind.
The switch to playing Alexis Sanchez instead of Olivier Giroud up front has definitely helped Walcott and Germany midfielder Mesut Ozil thrive too.
Sanchez runs in behind defences more, and Arsenal's build-up play is quicker. The Gunners are like speed kings on the break, particularly with Walcott and Spain full-back Hector Bellerin down the right.
Walcott is seeing the benefits of his hard work at the moment and is getting plenty of plaudits for it - but he needs to view this period as only the start of showing what he is capable of.
Getting pats on the back is nice but they can make you complacent and put you back in your comfort zone.
Theo needs to maintain this kind of desire and have the determination to not want to stop until he achieves something really special in an Arsenal shirt.
As a team, Arsenal have also improved significantly going forward compared with last season. Their number of shots on goal is up from 10.9 per Premier League game to 15.1 and their shot conversion rate has increased too - up to 23% from 16%.
That does not surprise me because his team's creativity is the thing Wenger works on the most, and it fell away in the second half of last season as their title challenge faltered.
Spain midfielder Santi Cazorla was not available because of injury from November onwards and Ozil's assists dried up after Christmas  - he made 16 goals before the end of December and only three afterwards.
At the time, the concern and criticism from fans and the media was about the defensive side of things, but Wenger will have been more alarmed about what was happening at the top of the team - and he will have been working since the summer on putting it right.
At the moment, with their run of seven successive wins in all competitions and scoring 23 goals in the process, they are reaping the rewards.
Their six wins in a row in the league have come against teams you might expect them to beat - but it is important to remember they failed to do that last season, when they won only two of the corresponding fixtures.
They have taken 10 extra points from the same games this season, a return that would have seen them finish level on points with champions Leicester in 2015-16.
Last season, Arsenal won the mini-league between the top five, only losing one of those eight games.
Results against the so-called lesser teams was one of the things that cost them. This season, so far, they have found a way of beating them even when they do not play well.
They will go top above Manchester City, for about 24 hours at least, if they win at home to Middlesbrough on Saturday - which I would expect them to do.
Let's not get carried away, though. It is still so early in the season and we have seen plenty of spells like this before from Arsenal since they last won the title in 2004.
If they are going to go the distance this time then, like Walcott, the Gunners need to maintain the determination that has got them these results and also not lose their belief when things do go wrong.
He is not the only Arsenal player who cannot afford to become complacent just because things are going so well at the moment.
Martin Keown was speaking to BBC Sport's Chris Bevan.


The Pakistani military has carried out air strikes in tribal areas in the north-west of the country, killing at least 15 militants, officials say.

The raids destroyed nine militant positions in the Tirah Valley in Khyber district, the military said.
The strikes came after the Taliban stormed Karachi airport, in an attack that killed at least 30 people.
The Pakistani Taliban said Sunday's assault was in revenge for the killing of their leader last year.
"Nine terrorist hideouts were destroyed by early morning military air strikes near the Pakistan-Afghan border," the military said in a statement on Tuesday.
The Khyber tribal region, near the Pakistan-Afghan border, is believed to be a base for several militant groups and foreign fighters.
It is not clear when the air strikes took place or which militant group was targeted, the BBC's Shahzeb Jillani in Islamabad reports.
Late on Sunday, 10 heavily armed Taliban fighters attacked an area of Karachi's Jinnah international airport used mainly for cargo and private flights.
Security forces gained control in the early hours of Monday.
The airport reopened late on Monday.
Officials said at least 29 people were killed in the fighting which raged from Sunday into Monday, including all the militants. On Tuesday, officials said nine more bodies had been recovered from the airport.
The number included seven bodies found in the airport's cold storage facility. Officials said they were charred beyond recognition.
There were reports that the bodies belonged to a group of airport employees who were trapped in the facility after taking refuge from the attack.
Pakistan has been fighting an Islamist insurgency for more than a decade, with the Pakistani Taliban the main militant grouping.
The airport attack came against the backdrop of a major split in the Pakistani Taliban, and threats of retaliation following limited military operations against foreign militants in North Waziristan.
The brazen attack has brought the government of the prime minister, Nawaz Sharif, under renewed pressure to order tough action against the Taliban militants, says the BBC's Shahzeb Jillani.
The Pakistan government began peace talks with the Pakistani Taliban in March, but little progress has been made and the violence has continued, with Karachi a frequent target.
Correspondents say that given the violence, it seems clear that any pretence at a peace process is now over.


The new Airbus A350 XWB that is flying daily displays at the Paris Air Show can claim several engineering firsts.

One of these is that it has more 3D printed components than any other aircraft, about 1,000 on a plane that has only just gone into service.
Meanwhile, Raytheon has 3D parts on its missiles, while makers of drones are increasingly using them. And United Launch Alliance - a joint venture between Lockheed Martin and Boeing - has the parts on the rockets it sends into space.
No longer is 3D a novelty manufacturing process. It's going mainstream, underlined by the number of 3D-related firms at the Paris show and conference briefings being held on the sidelines.
And it has the potential to transform the aerospace industry's global supply chain and cost structure, producing parts faster, and which are lighter and mean less waste. It may also mean companies bringing more production back in-house.
The 3D components on the A350 XWB are mostly widgets and brackets, formed by fusing layer upon layer of resins  in machines that replicate computer-generated 3D models. (Metals and even glass can also be used).
So, we're talking about small routine parts here, rather than large structures - at the moment.
But don't dismiss the significance that 3D printing is playing, says Ian Risk, Airbus Group's head of innovations in the UK, where the aerospace giant makes aircraft wings.
"These components contribute a huge amount to the manufacturing process. Often, it's the fiddly parts that create delays in production," he said.
The size of the component being made is limited by the size of the printing machine.
Mr Risk doubts there will ever be a machine big enough to turn out a whole airframe. "But we are looking at wider applications," he said. "The scale of what we do will increase."
3D printing's biggest supporters talk of a future world in which machines will be sited at key locations across the globe, churning out components when needed - not stored in a factory somewhere awaiting delivery to factories.
Say, for example, an A380 super-jumbo is flying into Singapore and needs a new part. In our digitally connected world, a machine could be programmed to start printing even before the aircraft lands.
It sounds good in theory, and Mr Risk says that "agile manufacturing" will certainly reshape the industry's global supply chain and reduce lead times.
But there are plenty of hurdles, especially the issue of transmitting secure data across the world, he said.
While the holy grail of on-demand supply may be a little way off, John Schmidt, US-based managing director of aerospace and defence at consultancy Accenture, says printing is reducing lead times from months to weeks.
He says it's too far early to call the end of traditional manufacturing - machining, casting and injection moulding. But the technology and scale of 3D printing will inevitably improve, so it's only a matter of time before a tipping point is reached.
3D parts reduce weight on aircraft, and so improve fuel efficiency, he says. And making one 3D part often replaces the need to combine several smaller parts, reducing the need to carry inventory.
Part of a cooling system used by rocket maker ULA now uses 16 parts, where before it was 140. ULA also says it has cut costs on its latest Atlas rocket by $1m using 3D.
Mr Schmidt added: "3D is also ideal for industries with short production runs - like aerospace - as it maximises the cost advantages of smaller production runs." It also reduces waste, as the component is built up rather than cut from a block of material.
He predicts that one of the most significant impacts could be on aircraft design, especially as 3D offers the promise to produce more complex shapes. "It opens options to be innovative in ways that do not exist now; to build something the first time and at the right time," he said.
And wouldn't that be good news for plane makers, whose big industrial projects are frequently plagued by production delays and cost-overruns.
The US-Israeli company Stratasys makes 3D machines and supplies materials and composites used to build components.
Director Scott Sevcik predicts that within 10 years, about 40-50% of aircraft components will use printed materials. It's about 4% now. In 20 years, the vast majority of parts will have some form of 3D printed contribution.
The thermoplastic material that Stratasys supplied for ULA's rockets can operate in extreme heat and cold, as well as under intense vibration and speed. As with 3D components used in civil aircraft, they have to go through rigorous regulatory approval.
Mr Sevcik said the ULA parts are for interior use, but that if tests on Stratasys' plastic, called Ultem, go to plan then 3D parts could be used on the exterior of unmanned rockets with a couple of years.
"It is very hard now to think of anything that won't be printable at some point in the future," he said, given advances in technology and material science.


A pensioner who admitted sexually assaulting a six-year-old girl has been fined Â£2,000 for the abuse.

Stuart Cowie, who was extradited from South Africa to face a hearing at Edinburgh Sheriff Court, admitted carrying out the assault in 2012.
The court heard that the 75-year-old was caught molesting the child by his wife.
In addition to fining him, Sheriff Kenneth McGowan placed him on the sex offenders' register for five years.
The court was told that Cowie and his wife Margaret had flown to Edinburgh from their South African home just ten days prior to the incident in October 2012 and were staying with the girl's parents.
Fiscal depute Kim Schofield said: "On October 7, around 5.30pm the accused was sitting in the TV room with the girl, who at the time was six-years-old.
"They were both sitting on the sofa and the accused placed his hand down the girl's trousers."
Mr Schofield said Cowie then exposed himself to the child. He added: "At which point, his wife walked into the room and saw the accused with his trouser's zip open and asked the girl to leave (the room).
"His wife later confronted him about what she had seen, saying she had seen his zip open. He replied she was 'talking nonsense'.
"While this conversation was ongoing, the mother of the child walked past the room and heard the argument. She heard Cowie's wife say 'I saw you with your zip down while the girl was there'."
The girl's mother then confronted Cowie about the attack, who responded by telling her: "I don't know what came over me - I just started fooling around."
Cowie was thrown out of the house by the child's parents and fled back to South Africa.
The court heard that Cowie sent two letters to the family begging for forgiveness for his "inexcusable behaviour", adding that he was "deeply ashamed" at what he had done.
George Henry, defending, said Cowie's family life had "disintegrated" since he admitted the abuse.
Mr Henry also said that upon his arrest in South Africa, his client had spent two nights in custody before being returned to the UK and then spent a further five nights on remand in HMP Edinburgh.


Former Liverpool striker Iago Aspas scored twice as Celta Vigo beat La Liga rivals Deportivo La Coruna 4-1 in the Galician derby.

Aspas scored from the penalty spot on the hour to put Celta 2-1 up after Raul Albentosa had cancelled out Hugo Mallo's opener.
Fabian Orellana added a third for Celta in the 78th minute before Aspas, 29, sealed the win seven minutes from time.
Aspas scored once in 15 appearances for Liverpool in the 2013-14 season.
Liverpool signed Aspas from Celta for £7m in June 2013 but he struggled to make an impact and was sold to Sevilla.
He rejoined Celta for a second spell in June 2015 and scored 14 goals in 35 appearances in La Liga last season.
Match ends, Celta de Vigo 4, Deportivo de La Coruña 1.
Second Half ends, Celta de Vigo 4, Deportivo de La Coruña 1.
Attempt missed. Pedro Mosquera (Deportivo de La Coruña) header from very close range is too high. Assisted by Celso Borges following a corner.
Attempt missed. Celso Borges (Deportivo de La Coruña) header from the centre of the box misses to the left. Assisted by Faycal Fajr with a cross following a corner.
Corner,  Deportivo de La Coruña. Conceded by Pablo Hernández.
Attempt blocked. Florin Andone (Deportivo de La Coruña) right footed shot from a difficult angle on the right is blocked. Assisted by Carles Gil.
Nemanja Radoja (Celta de Vigo) wins a free kick in the defensive half.
Foul by Marlos Moreno (Deportivo de La Coruña).
Substitution, Celta de Vigo. Pione Sisto replaces Orellana.
Cabral (Celta de Vigo) wins a free kick in the defensive half.
Foul by Florin Andone (Deportivo de La Coruña).
Substitution, Celta de Vigo. Giuseppe Rossi replaces Iago Aspas.
Foul by Cabral (Celta de Vigo).
Florin Andone (Deportivo de La Coruña) wins a free kick in the attacking half.
Corner,  Deportivo de La Coruña. Conceded by Facundo Roncaglia.
Goal!  Celta de Vigo 4, Deportivo de La Coruña 1. Iago Aspas (Celta de Vigo) left footed shot from the left side of the box to the bottom left corner. Assisted by Sergio Álvarez.
Offside, Celta de Vigo. Pablo Hernández tries a through ball, but Iago Aspas is caught offside.
Nemanja Radoja (Celta de Vigo) wins a free kick on the left wing.
Foul by Carles Gil (Deportivo de La Coruña).
Substitution, Deportivo de La Coruña. Celso Borges replaces Guilherme.
Goal!  Celta de Vigo 3, Deportivo de La Coruña 1. Orellana (Celta de Vigo) header from the centre of the box to the bottom left corner. Assisted by Jonny with a cross.
Attempt saved. Orellana (Celta de Vigo) right footed shot from outside the box is saved in the centre of the goal.
Pedro Mosquera (Deportivo de La Coruña) is shown the yellow card for a bad foul.
Orellana (Celta de Vigo) wins a free kick in the attacking half.
Foul by Pedro Mosquera (Deportivo de La Coruña).
Substitution, Celta de Vigo. Marcelo Díaz replaces Theo Bongonda.
Substitution, Deportivo de La Coruña. Carles Gil replaces Ryan Babel.
Delay over. They are ready to continue.
Delay in match Hugo Mallo (Celta de Vigo) because of an injury.
Offside, Deportivo de La Coruña. Faycal Fajr tries a through ball, but Guilherme is caught offside.
Orellana (Celta de Vigo) is shown the yellow card.
Foul by Orellana (Celta de Vigo).
Fernando Navarro (Deportivo de La Coruña) wins a free kick on the left wing.
Attempt blocked. Pedro Mosquera (Deportivo de La Coruña) left footed shot from outside the box is blocked.
Corner,  Deportivo de La Coruña. Conceded by Sergio Álvarez.
Pablo Hernández (Celta de Vigo) is shown the yellow card for a bad foul.
Foul by Pablo Hernández (Celta de Vigo).
Marlos Moreno (Deportivo de La Coruña) wins a free kick in the attacking half.
Attempt missed. Faycal Fajr (Deportivo de La Coruña) right footed shot from outside the box is close, but misses to the left following a set piece situation.
Attempt blocked. Guilherme (Deportivo de La Coruña) right footed shot from outside the box is blocked.


The 25th official James Bond film will be released in November 2019, producers have confirmed.

The currently-untitled movie will be written by Neal Purvis and Robert Wade, who worked on the last six films.
But it has not yet been announced whether Daniel Craig will return to play Bond for the fifth time.
The BBC understands the actor has not yet signed a contract, but the New York Times reports his return to the role is a "done deal".
Bond 25 will be released in the US on 8 November 2019, with a slightly earlier release in the UK and the rest of the world.
The film is set to be produced by Michael G Wilson and Barbara Broccoli.
Skyfall, Craig's third Bond film, became the highest-grossing film of all time in the UK after its release in 2012, but it has since been toppled by Star Wars: The Force Awakens.
Follow us on Facebook, on Twitter @BBCNewsEnts, or on Instagram at bbcnewsents. If you have a story suggestion email entertainment.news@bbc.co.uk.


A kitten - dubbed Britain's luckiest - is recovering after being rescued from a garden fire.

The cat, named Phoenix by rescuers, had severe burns to her face and body after being spotted trapped under blazing rubble in Sunderland in June.
She has been cared for by RSPCA staff at Felledge, near Chester-le-Street and is expected to make a full recovery.
Phoenix, now 14 weeks old, still needs daily treatments but is now playing with other kittens, centre staff said.
No-one knows how she came to be trapped in the fire or if she had a previous owner.
Luka Atkinson, reception supervisor at RSPCA Felledge, said Phoenix was in a "really sorry state" when she arrived.
"The skin on all four of her pads was burnt off and the fur on her face, tummy and legs was singed - she was lucky to be alive," he added.
"It's definitely been tough seeing Phoenix go through her recovery and she's not out of the woods yet, but the whole time we have had her here she has been eating really well, drinking, and has loved cuddles and playing, so we knew we had to keep going with her treatment and give her a chance.
"She is such a happy little thing and runs riots with the other kittens at our centre... She really is the luckiest kitten in Britain."


Several Tube stations in east London have been rezoned to recognise the capital's "shifting economic map".

Eight stations including Stratford and West Ham have been rezoned from Zone 3 to Zone 2/3.
It means the stations will be regarded in Zone 2 or 3 depending on which way the passenger is travelling, giving the cheapest travel option for the journey.
The Mayor of London said it was hoped 100,000 people per week would benefit from the change.
How a Zone 2/3 boundary station works
According to Transport for London a passenger would always pay the cheapest fare depending on which direction they were travelling in.
For example, if they were travelling from Zone 6 to Stratford they would pay a Zone 3-6 fare, whereas if they were travelling to or from Zone 1 from Stratford they would pay a Zone 1-2 fare.
The other stations that have been rezoned are Stratford High Street, Stratford International DLR station, West Ham, Canning Town, Star Lane and Abbey Road.
Sir Robin Wales, the Mayor of Newham, said: "We've been campaigning for this for some time. The truth is London's moving eastwards... and it's sensible to reduce the cost of travel.
"It's going to encourage people to come to Stratford, West Ham and Canning Town, which will be great."
Transport for London has made the changes as part of its 2016 plans, which include a ticket price hike of 1% in line with the July Retail Price Index and enabling children to travel for free on National Rail services in the capital.
The changes also include it becoming possible to use an Oyster or contactless card for  journeys between London and Gatwick Airport on Southern, Gatwick Express and Thameslink services from 11 January.


A bill which will lead to changes in NI's alcohol licensing laws will be debated later on Tuesday.

The bill at Stormont will mean some liberalising of the law but does not go as far as many in the hospitality industry would have liked.
The main change is that pubs and nightclubs will be able to serve alcohol for an extra hour, until 02:00, up to 12 times a year.
The hospitality industry wanted late licences to be available every weekend.
The other main change is the extension in "drinking-up time" from half an hour to an hour.
Most restrictions around Easter drinking will stay in place.
The only change is that on the Thursday before Easter serving time will be extended from midnight to 01:00.
The law will also be tightened in some areas - supermarkets will face restrictions on where they can place in-store advertising.
The current voluntary code of practice for alcohol retailers will also be replaced with a statutory code.
The bill is expected to become law by the middle of 2017.


Irish naval ship LÉ Eithne has been told by Italian authorities to take 399 migrants to Taranto port in Italy.

On Sunday morning, the ship rescued 310 people on a barge and a further 89 were lifted off two inflatable crafts, 75km north of Libya, that afternoon.
In the past two days, LÉ Eithne has saved more than 500 people attempting to cross the Mediterranean from Africa to Europe.
LÉ Eithne will be deployed in the Mediterranean for up to six months.
Italy's coastguard said nearly 3,500 migrants were rescued in total on Sunday from 15 boats off the coast of Libya.
The International Organisation for Migration has praised the Irish Naval Service for its efforts.
To date, it has brought more than 1,100 people to safety in the Mediterranean.
It is estimated that more than 1,600 people have drowned so far this year trying to make the crossing.
Many are fleeing war in Libya, where so-called Islamic State fighters are terrorising the population, fuelling instability in the war-torn country.


The mother of a British child who went missing in Greece in 1991 has said the case of a girl allegedly abducted by a Roma couple has given her "fresh hope".

A blonde girl called Maria, aged five or six, was found at a Greek Roma camp last week, and a couple who claimed to be her parents were arrested.
Kerry Needham, whose son Ben was abducted in Kos aged 21 months, said she always believed gypsies took Ben.
She said Greek police must now "investigate the gypsy theory further".
Ms Needham said Maria's case had given her family "fresh hope and maximum publicity", and she remained certain Ben would be found.
She told the BBC Greek authorities had suggested it would be "impossible" to conceal a blonde-haired child in a gypsy encampment, but the case of Maria - who has blonde hair - proved that wrong.
She said the family had repeatedly claimed Ben had been taken by gypsies, but Greek police had always "strongly denied" the possibility.
Ben, from Sheffield, went missing while on a family holiday in Kos.
Ms Needham said she was in contact with South Yorkshire Police, but the force said there appeared to be "no direct correlation" between the cases of her son and Maria.
A spokesman added: "No investigation is currently being carried out by the force in light of this recent case and officers from South Yorkshire Police will only become involved should authorities in Greece require our assistance."
The girl named Maria was found in central Greece when police, who were carrying out a raid looking for drugs and weapons, noticed the lack of resemblance between the child and the couple claiming to be her parents.
Officers checked documents, and DNA tests later revealed Maria was not related to the couple.
A fake birth certificate suggested she was four years old, but the charity now caring for her says medical examinations have revealed she is probably five or six.
A lawyer for the Roma couple has said Maria was given to them, not kidnapped.
Meanwhile, a spokesman for Kate and Gerry McCann, parents of Madeleine McCann, said the case of Maria had given them hope, according to the Daily Mirror.
Madeleine was three years old when she was abducted in Portugal in 2007, and police investigating her disappearance have received more than 2,400 calls since an appeal on the BBC's Crimewatch programme was broadcast last week.


A theme park has asked people not to scream on a new rollercoaster ride because it's too noisy.

The owners of Big Sheep in north Devon said they erected a warning sign after people living nearby raised concerns over the new ride.
The 400m-long attraction, the Big One, opened at the park this Easter.
Owner Rick Turner said the message to customers was "unless they're absolutely petrified, please please don't scream too much".
The planning process for the ride in the village of Abbotsham had taken four years, and a group of local people had got "very very animated" over the prospect of loud noise coming from the attraction, he told the BBC.
Over Â£200,000 has been spent building a large noise reduction bank in the middle of the ride, and legal expertise was sought about the noise levels.
Hugh Bone, chair of Abbotsham parish council said he was "pleased" the sign was there, after villagers asked the council to control "the amount of sound" coming from the theme park.
Local people "do worry" about the noise, he said, particularly on weekends "when there may be funerals or weddings taking place" in the nearby church.
Mr Turner said Big Sheep had been in the village for 30 years and it was "somewhat galling" when new residents decided to complain after they had moved to the village.
However, he said the park tried its best to reduce noise for neighbours, and he hoped the sign would discourage riders from "shouting excessively", even if some would inevitably "squark".
This is the second placard to go up at the park - one next to a flying chair ride reads: "We love our neighbours, no screaming please".


Australia's new PM Malcolm Turnbull is facing fresh calls to shut down offshore migrant detention centres.

Australian of the Year and domestic violence campaigner Rosie Batty said on Thursday the "unsafe" camps must close.
Nearly 450 staff at Mr Turnbull's former university have also expressed concern about claims of torture by government employees and contractors.
Australia intercepts all irregular boat migrants and holds them in camps in Nauru and Papua New Guinea.
Mr Turnbull has defended the rules, a central policy of former Prime Minister Tony Abbott, by saying they are tough but save lives.
In a letter to Mr Turnbull, Ms Batty said those detained in offshore centres needed care, instead of punishment.
"The centres are, by their very design, unsafe and dangerous places. These centres cannot be patched up," she said.
The academics, meanwhile, said there was "overwhelming" evidence that "repugnant acts" including torture and abuse had been carried out the camps.
This week, the Australian Broadcasting Corp aired allegations made by a Somali woman who said she was raped by two men on Nauru - and that it took police on the Pacific island four hours to respond.
Is Australia's Cambodia solution 'an expensive joke'?
Australia's controversial asylum policy
Mr Turnbull said the rape claims raised in the report were "very alarming", but defended the government's stance on border security.
"The one thing we know is these policies, tough though they are, harsh though they are in many respects, actually do work, they save lives," Mr Turnbull said.
"We're taking a number of steps to work closely with the Nauru government to ensure the safety and the security of all the refugees living in that community."


A voluntary redundancy scheme for public servants could be opened up to help Stormont balance its budget.

Peter Robinson thinks such a voluntary scheme would save £160m a year.
The first minister told a DUP event on Thursday that he expected "you would be knocked over in the rush" if such a scheme opened.
Sinn Féin has not disagreed that such a scheme is on the cards. The executive agreed a loan of up to £100m from the Treasury on Thursday.
Finance Minister Simon Hamilton said the executive still faced an "incredibly difficult budget situation" that was exacerbated by the executive's failure to reach a deal on welfare reform.
"The entire executive recognises that we're facing immense challenges moving forward," he said.
"At our meeting on Wednesday, there was agreement across all of the parties that the head of the civil service would go away and produce a report and a plan for the executive to consider that would look at the restructuring of our whole public sector.
"That will look at issues around the number of civil servants and public servants that we have, issues around pay as well and we will consider that in the light of what the head of the civil service brings back to us."
Analysis: BBC News NI Economics & Business Editor John Campbell
On the most recent figures, for June 2014,  there are 212,000 employees in the Northern Ireland public sector.
About 74,000 of those work in the health service and another 65,000 work in education.
The numbers have been coming down over the past five years - in June 2009 the total was 226,000.
In the Police Service of Northern Ireland (PSNI) for example, numbers have decreased from 11,000 to fewer than 10,000.
But there have been steeper falls in other parts of the UK.
A paper circulating at Stormont examines the change in public sector employment between 2010 and 2013.
It shows a fall of less than 4% in Northern Ireland, compared to a drop of almost 8% in Scotland and more than 10% in England.
Education Minister John O'Dowd said his party would await the outcome of those discussions.
"We will wait on the report from the head of the civil service after the discussions with the union, but the key word is voluntary," he said.
"At this stage no-one is envisaging that there will be forced redundancies upon anyone.
"There has not been a voluntary redundancy scheme within the civil service for many, many years and there is a suggestion that if a voluntary redundancy scheme came forward that it would be quite popular and that it would attract the numbers that would be required to reduce costs across the public service.
"We will take a look at the terms and conditions of (any) voluntary redundancy scheme and if we're satisfied with it, we will support a voluntary redundancy scheme after all those measures have taken place."
The number of public sector jobs in Northern Ireland has been falling slowly but now it looks like the pace will pick up.
The deal to secure the loan of up to £100m from the Treasury was brokered by the Democratic Unionist Party with the Chancellor, George Obsborne.
It means extra cash for departments, including £60m for the Department of Health and almost £30m for the Department of Justice.
However, the arrangement has been criticised by other parties as an "expensive sticking plaster".
The Treasury had been asked to supply Stormont with a one-off loan of between £100m and £150m to ease its budgetary crisis.
It is understood that Peter Robinson and Finance Minister Simon Hamilton made the proposal to the chancellor.
Mr Robinson said the loan was conditional on Stormont agreeing a draft budget for 2015/16 by the end of October.
The loan will ensure Stormont does not breach its spending limits by more than £200m at the end of the financial year.
However, it will increase the amount Stormont will owe the Treasury next year.
Northern Ireland's failure to implement welfare reform means the executive will incur £87m in penalties this year and another £114m next year - those penalties might be waived if the parties reach a deal in the near future.
It is also understood that welfare reform is not part of the deal with the Treasury, but instead will feature in the planned political talks due to begin next week.


Assembly members have voted against a move to ban smacking children in Wales.

Cardiff North AM Julie Morgan had proposed a change to the Violence against Women, Domestic Abuse and Sexual Violence Bill to remove the defence of "reasonable punishment".
It would have made it illegal in Wales for parents to hit their children but the amendment from Labour's Ms Morgan was lost by 36 votes to 16.
The Welsh Labour government opposed the measure.
It had rejected calls for a free vote on the issue.
However Ms Morgan and another Labour backbencher, Christine Chapman AM, voted against the party.
Introducing the amendment, Ms Morgan told AMs it was about "finally doing right by the children of Wales".
"How can we possibly justify saying to children 'no - it's not right for your dad to hit your mum, or your mum to hit your dad. But it's ok for either of them to hit you'," she said.
"It's a ridiculous and it's an inconsistent message, and not only does it not make sense, it also leaves children vulnerable within the home."
The Public Services Minister Leighton Andrews said "there are many good arguments for ending the defence of reasonable punishment but the government has been clear that this bill is not the right place to address this issue and we remain strongly of that view".
AMs were debating and voting on several amendments to the bill on Tuesday.
A move to make schools offer lessons on healthy relationships was narrowly rejected.
The Welsh government has ruled out any change to the law on smacking children before next year's assembly elections.
In October 2011, assembly members voted in principle to remove the defence of "reasonable chastisement" although they did not have the power at that time to impose a ban on smacking.


Judoka Colin Oates says he is considering his future after losing in the 2016 Rio Olympic -66kg first round.

Media playback is not supported on this device
The 2014 Commonwealth Games champion lost to France's Kilian Le Blouch after a penalty in golden score.
"People say to me 'you're only 33', but 33 in judo is old. In February I was almost on the verge of not wanting to come," the Norfolk athlete said.
"I had a good few months, won European silver, but now it's time to reassess and see what comes next."
He continued: "I never say never (about competing at Tokyo 2020). I think my staff may say it's a bit out of reach, maybe British Judo will look to youth for the next four years and maybe they're right to do so."
Neither Oates nor his opponent scored a point in the match, and Oates was eight seconds from victory before being penalised by the referee to level the scores and taking it to a golden score, where he was penalised again.
Oates continued: "I left it down to the referees, unfortunately. It was a scrappy fight, it's his style of fighting, he doesn't really want to score, he wants to win on shidos (penalties) and I played into that a little bit.
"The worst thing is I've been feeling the best I've ever felt going into these Olympics but I've not produced the performance I think my training and work ethic has deserved."


A German court has ruled that Motorola Mobility infringed a Microsoft patent which allows long text messages to be divided into parts and then reassembled by receiving handsets.

It marks the first patent ruling against Google since it completed its takeover of Motorola.
Microsoft can now demand a German sales ban of Motorola products, although it signalled it would prefer a licence fee.
Google said it may appeal.
Google's chief executive had previously said that his firm bought Motorola and its patents "to better protect Android from anti-competitive threats from Microsoft, Apple and other companies".
Microsoft and Motorola have repeatedly clashed this month over a series of patent disputes.
Motorola won the right to order the recall and destruction of Xbox 360 games consoles and Windows 7 system software in Germany at the start of May.
A judge at the International Trade Commission (ITC) subsequently recommended there should also be a Xbox import and sales ban in the US.
However, another Seattle judge has ordered Motorola to hold off from enforcing any such bans until it ruled on a related complaint.
Microsoft won a separate patent victory against Motorola earlier this month when the ITC ruled that the handset maker's Android-based devices infringed an appointment scheduling patent owned by the Microsoft.
The Windows software maker has already forced other firms including Samsung, HTC and others to pay it for the use of its innovations within Google's system software.
The latest ruling
          centres on a European patent
 named "communicating multi-part messages between cellular devices using a standardised interface".
It is designed to tackle the problem that SMS messages were designed to offer a maximum of 160 characters.
It describes a way of "fragmenting" a longer text into smaller parts and then "reassembling" it within an application on the receiver's handset.
Florian Mueller, a patent consultant who advises Microsoft, was at the ruling made at a court in Munich.
He blogged that Google could find it difficult to work around the problem if it refuses to pay a licence fee.
"Since this patent covers operating system-level functionality, the modifications 'Googlerola' would have to make to Android... would lead to significant complications,"
          he wrote
.
"Android apps that make use of Android's messaging layer would have to be rewritten, and some functionality that Android used to provide to app developers would have to be implemented by the affected applications themselves."
A statement from Google said: "We expect a written decision from the court on 1 June and upon review, will explore all options including appeal."


Almost a third of patients in England and Wales are being given the wrong initial diagnosis after a heart attack - with women having a far higher chance of being affected, a study suggests.

University of Leeds research examined NHS data on about 600,000 heart attack cases over a period of nine years.
Women were 50% more likely than men to have an initial diagnosis different from their final diagnosis, it said.
NHS England said it was working to improve the diagnosis of heart attacks.
The British Heart Foundation (BHF) is urging people to be aware of the symptoms of a heart attack.
The study, which appears in the European Heart Journal - Acute Cardiovascular Care, looked at the UK national heart attack register and was carried out between April 2004 and March 2013.
It involved 243 NHS hospitals in England and Wales which cared for patients who were aged between 18 to 100 years old when they were admitted.
Researchers found that 198,534 patients were initially misdiagnosed.
Up to 28,000 women die from heart attacks each year in the UK, according to the BHF. There are also about 275,000 female heart attack survivors in the UK.
Dr Sarah Clark, consultant cardiologist at Papworth Hospital, told BBC Radio 4's Today programme that the symptoms of a heart attack can be "very subtle" and, in her experience, men are more likely to report problems than women.
"I have to say I think women tend not to present as frequently as men do, they tend to play down their symptoms... and present later," she said.
Lisa Price, from Bolton, had an ankle operation which resulted in a blood clot which led to a heart attack.
She said women should be made more aware of the differing symptoms.
"The symptoms are not falling to the floor and clutching your chest, they are very different," she said.
"At first the feeling was a real tightness and a crumbling of my ribcage - it was as if I had a small child sitting on me - a child that just would not move. There was such a heavy weight.
"As the actual symptoms progressed it actually turned into a burning. It was as if a burning cannonball had actually been pushed through me and I could feel a huge hole burning right through from my front to my back."
Doctors initially said her symptoms were a result of the operation and told her to take paracetamol, she said.
Although the chest pain is often severe, some people may only experience minor pain, similar to indigestion. In some cases, there may not be any chest pain at all, especially in women, the elderly and people with diabetes.
Source: NHS
The BHF, which part-funded the study, says heart attacks can be classified into two main types - STEMI (ST segment elevation myocardial infarction) and NSTEMI (non-ST segment elevation myocardial infarction).
NSTEMI, the more common type, involves a partial blockage of one or more arteries and can cause serious damage to the heart muscle.
A STEMI, which the NHS calls the "most serious type of heart attack", occurs when there is long interruption to the blood supply.
"This is caused by a total blockage of the coronary artery, which can cause extensive damage to a large area of the heart," the NHS explains.
Women who had a final diagnosis of STEMI had a 59% greater chance of a misdiagnosis compared with men, while women who had a final diagnosis of NSTEMI had a 41% greater chance of a misdiagnosis when compared with men.
The BHF's associate medical director Dr Mike Knapton said the diagnosis differences were "alarmingly high" but said better tests were being developed for female heart attack diagnoses.
"This new study highlights the current scale of the issue and confirms more research is urgently needed into tests that will enable earlier and more accurate diagnosis of a heart attack, particularly in women," he added.
Researcher Dr Chris Gale said: "We need to work harder to shift the perception that heart attacks only affect a certain type of person.
"Typically, when we think of a person with a heart attack, we envisage a middle aged man who is overweight, has diabetes and smokes.
"This is not always the case - heart attacks affect the wider spectrum of the population - including women."
An NHS England spokesman said: "Survival rates for heart attacks are the best they have ever been and swift diagnosis and treatment is key to this.
"We are working hard to continually improve tests for accurately diagnosing heart attacks in both men and women so that correct treatment can begin without delay, ensuring the best possible recovery for patients.
"We are also working to increase awareness of signs and symptoms of heart attack amongst both the public and healthcare professionals as this will help speed up diagnosis."


Britain's Gordon Reid completed a career Grand Slam in the wheelchair men's doubles by winning the Australian Open in a final-set tie-break.

Reid, alongside Belgian Joachim Gerard, won 6-3 3-6 1-0 (10-3) against fellow Briton Alfie Hewett and Gus Fernandez.
The Scot, 25, won Wimbledon last year alongside Hewett, after previously winning the US and French Open (twice).
"It was a last-minute decision to play with Jo but one that has paid off," Reid said.
"I don't think any one of us played our best tennis today but we upped our level when it mattered."
Find out how to get into tennis in our fully inclusive guide.
There could be more British success in Melbourne after Andy Lapthorne reached the quad singles final.
Lapthorne, 26, will meet Australia's Dylan Alcott, who beat him in the 2016 Rio Paralympics final, on Rod Laver Arena on Saturday after semi-final opponent Heath Davidson pulled out through injury.
Lapthorne is aiming for a double after teaming up with American David Wagner on Thursday to win his fifth Australian Open quad doubles title.


Guinea-Bissau's President Jose Mario Vaz has dismissed the government following a rift with Prime Minister Domingos Pereira.

The two men are said to have disagreed on a number of issues including the use of aid money and the return to Guinea-Bissau of a former army chief of staff.
The West African state returned to civilian rule in June last year.
With a history of coups, no elected leader has served a full term since independence from Portugal in 1974.
Many senior military officers have also been accused of turning the country into a narco-state as it a major hub for cocaine smuggled from Latin America to Europe.
BBC Africa's Zenaida Machado says the announcement follows weeks of tension between the president and the prime minister.
In a televised address, Mr Vaz said a simple reshuffle would not be sufficient to solve the problem.
"It is public knowledge that there is a crisis undermining the proper working of institutions," he said.
The UN Security Council has asked the leaders to resume dialogue.
Earlier in the week, Portugal warned that development aid could be at risk if the country slipped back into instability.
One of the dismissed ministers said that the consequences of the sackings were "unpredictable".
"If the state does not work, if people are in the street, we don't know what can happen," Angelo Regala, the former communications minister, told BBC Afrique.
The African Union representative to Guinea-Bissau, Ovideo Pequeno, said that the military was unlikely to get involved.
He told the BBC's Focus on Africa programme that top commanders had said they consider it a political issue, which was not their concern.
Guinea-Bissau:
Read more:
Hooked: The story of Africa's first narco-state in graphic novel style
The challenges faced before 2014 election
Guinea-Bissau profile


A search has resumed of the River Ness in Inverness after police received reports of a man falling from a bridge on Sunday.

RNLI Kessock, coastguard personnel and police made searches of the river and Inverness Harbour on Sunday night after the alarm was raised at 17:20.
Police Scotland said the man was reported to have gone into the river at the Greig Street footbridge.
The man is believed to be in his 40s and wearing dark clothing, police said.
The latest search has also involved checks of Inverness' harbour and marina.
It had been hoped a coastguard helicopter would join the effort, but bad weather prevented the aircraft and crew being involved.


The Assembly Commission has issued a joint statement about MLA expenses with Stormont's expenses watchdog, the Independent Financial Review Panel.

It acknowledges the "negative impact which recent publicity has had on public confidence".
The statement recognises differences that remain over the interpretation of the panel's determination on expenses in March 2012.
It follows a week of disagreements over expenses payments.
However, the statement says that both bodies are "committed to working together" to address those differences.
The panel will publish its next determination in March while the Assembly Commission, a cross-party group which manages assembly matters, will publish a new Members' Handbook based on that determination.
The Independent Parliamentary Standards Authority (IPSA) will examine the new handbook to "quality assure" it before it is approved by the assembly.
Earlier it emerged that assembly members claimed for work carried out by exterior research companies until 2014.
The Independent Financial Review Panel (IRFP) maintains that none of these payments should have been made after April 1 2012.
Such expenses are at the centre of the row between the Stormont watchdog and the Assembly Commission.
The current assembly members' handbook still allows an MLA to claim for third party research.
BBC Radio Ulster's Stephen Nolan programme revealed on Friday that payments to such third parties continued into the 2014/15 financial year.
The IFRP said in a statement on Thursday it did not believe it made a mistake in a ruling banning such payments in 2012.
However, the Assembly Commission said that it had applied the ruling correctly.


Inverness Caledonian Thistle manager Richie Foran has made an offer to recruit former Motherwell defender Louis Laing.

Laing, 23, is a free agent and has other offers after leaving Well, who recently loaned him to Notts County.
He previously played for Sunderland, Wycombe and Nottingham Forest.
"It would be to the end of the season and he has a couple of options, once he hears back then we'll know," said Foran.
"He'd be a good one to bring in as we've got a couple of suspensions coming up."
Caley Thistle, who have defender Josh Meekings out for two months following knee surgery, visit Celtic in Saturday's Scottish Cup tie before resuming their Premiership campaign away to Hearts on 18 February.
The Highlanders are three points adrift at the bottom of the division with 14 league games remaining.
"We go there [to Celtic Park] with no pressure - probably the only Premiership team without pressure," added Foran.
"Celtic are through in most people's minds. You're away from the stresses of the league campaign and the boys are looking forward to it.
"Given where we are in the league, it could be draining for some players. Some it will affect, some it won't. I had a go publicly last week and got the response I was after [in the 2-2 draw with Dundee].
"You've got to keep that mindset positive and your breaks will come.
"Celtic are playing with extra pressure on their shoulders going for the treble."


In Britain, Argentine Diego Simeone is best remembered as the man whose reaction to a petulant kick by David Beckham resulted in the England star famously being sent off during a World Cup game in 1998.

That is a harsh reflection on his playing career, though, because Simeone was a magnificent midfielder, winning 106 international caps and starring in Serie A for Inter Milan and Lazio as well as guiding Atletico to a league and cup double in 1996 (their most recent La Liga triumph).
And now, Simeone is carving a new career as one of the game's hottest managerial properties, with his approach to coaching mirroring the blend of winning attitude and technical aptitude that characterised his playing days.
If you asked Diego Simeone how his Atletico Madrid team have overcome all the odds to progress to the Champions League semi-finals, where they will face Jose Mourinho's Chelsea, as well as topping La Liga with just six games remaining, he would provide you with a simple answer: "Hard work and humility."
Indeed, that is exactly the mantra he has been preaching on a weekly basis this season, as the football world continues to wonder when - or if at all - his steamroller of a team will finally run out of puff.
Until recently, most people assumed it would simply be a matter of time. When, not if. But Wednesday's famous victory over Barcelona, where Atletico succeeded in knocking the Catalan team out of the Champions League before the last four for the first time since 2007, sent a loud and clear message: Atletico Madrid are for real.
To a great extent, Simeone's assessment of his Atletico team's greatest strengths - hard work and humility - is absolutely right.
Atletico were only four points above the La Liga relegation zone when Diego Simeone became coach in December 2011. Within 18 months he had guided them to the Europa League, Uefa Super Cup and Copa del Rey titles.
The discipline, intensity and sheer, uncompromising effort of their play is unrivalled. That was never more evident in the opening stages on Wednesday, when Atletico's whirlwind of attacking pressure simply blew Barcelona away, resulting in Koke netting the only goal of the game and David Villa thumping shots against the woodwork twice inside the opening 20 minutes.
Hard work and humility - as well as, to use Simeone's other favourite phrase, going from game to game - have allowed Atletico's bunch of largely unheralded journeymen, none of whom (with the exception of Villa) were superstars before they arrived at the Vicente Calderon, to barge their way without an invitation into the upper echelons of world football.
For any football fan who has become cynical about the modern game's tendency to be ruled by huge dollops of money, Atletico's unstoppable rise has been a breath of fresh air.
In the days of Arab sheikhs, Russian oligarchs and American business tycoons, low-budget teams like Atletico simply aren't supposed to do this well. Yet here they are, with less than six weeks of the season remaining, still in strong contention for the two most prestigious prizes on offer.
That is, indeed, largely down to the relentless work ethic instilled by Simeone. But it would be very wrong to suggest that Atletico's current success is simply down to the fact that they run around a lot, because there is also a huge amount of quality and intelligence within their ranks.
That starts on the training ground, where Simeone and his gruff assistant Mono Burgos prepare the perfect tactics to suit their team's strengths.
Under Simeone's instruction, Atletico are defensively disciplined, unsurpassably organised and play with great game awareness, knowing when to press ferociously in numbers and when to sit deep, waiting for the right opportunity to pounce upon their hapless opponents and launch a rapid, pinpoint counter-attack.
As the eloquent Argentine boss explained in the build-up to his team's latest triumph, Barcelona's strength lies in controlling possession; Atletico's lies in controlling space.
Simeone's attention to detail and his ability to clearly communicate his plans ensures that his players have mastered the art of playing the game where they want to, while simultaneously forcing their opponents into areas where they feel uncomfortable.
More than anything, though, Simeone's unbounding positivity and unshakeable belief that good habits, when consistently applied on a day to day basis, will lead to winning performances has succeeded in completely turning Atletico's image on its head.
For years, Madrid's second team suffered from a severe inferiority complex as neighbouring Real ruled the roost and the rest of Spain derided them as hapless bunglers who always managed to somehow mess everything up.
That reputation was most famously captured in a notorious television advert, when a forlorn young boy asked his frowning father: "Porque somos del Atleti?" Why are we Atleti fans? It was a sort of Spanish equivalent to "Accrington Stanley…who are dey?" and illustrated the inescapable sense of inevitable doom which habitually engulfed Atletico fans as they lurched from disaster to disaster.
Under Simeone, Atletico are finally shattering that conception; their manager is even an image of vibrant self-belief as he prowls the touchline during games, constantly turning to the crowd and vigorously urging them to applaud the players for their wholehearted effort.
When referee Howard Webb blew the final whistle at the Vicente Calderon on Wednesday, tremendous scenes of jubilation were unleashed, with the home fans - chanting and singing with a relentlessness almost matching their team - refusing to leave the shaking stadium until their heroes re-emerged from the tunnel to embark upon a celebratory lap of honour.
As the players finally gave way to those demands and dragged their weary bodies back onto the pitch, to be sportingly saluted even by the travelling Barcelona fans, one man was conspicuous by his absence. Diego Simeone was apparently nowhere to be seen.
But he was there all right, hiding on his own at the back of the dugout, quietly watching the scenes of celebration he had helped to create with obvious pride, seemingly struggling to force back tears. After the hard work, the humility.
Former Liverpool and Republic of Ireland forward Michael Robinson, who finished his playing career in Spain and is now the country's foremost television pundit, concluded his rhapsody over Atletico's performance by enthusing: "It's impossible not to admire them."
Robinson is exactly right. "Why are we Atletico fans?" Right now, the more pertinent question is why anyone wouldn't be.


In the centre of Arkhangelsk stands a curious monument: a Mark V British tank dating back to just after the Russian Revolution.

Many here see it as a symbol of foreign aggression and western interventionism. It was captured after British-led forces had landed in northern Russia to try to fight the Bolsheviks.
A little more than 20 years later, British tanks were heading back to Arkhangelsk (the town which was better known in Britain as Archangel). This time though, the Russians were more than delighted to see them.
The tanks, together with fighter planes, fuel, ammunition, raw materials and food, were among a string of emergency supplies to the Soviets from their Western Allies.
The Soviet Union had been invaded by Nazi Germany and the supply missions aimed to help the Red Army fight back.
But to get the goods to northern Russia, convoys of ships had to steer a treacherous course from the UK through the icy waters of the Arctic Ocean. Winston Churchill once described it as "the worst journey in the world".
"The Germans tried all sorts of tricks," recalls 86-year-old David Cottrell from Bristol, a gunner on a Royal Navy destroyer which had been escorting the convoys.
"The Germans would send in U-boats. Also, loads of aircraft. So you were being attacked by air and underneath.
"On occasion you did get several German destroyers out from Norway to intercept. On my second convoy, a German torpedo missed our ship by inches. It hit another vessel and sank it."
Bad weather was the other enemy - thick fog, pack ice and raging storms.
Between 1941 and 1945, the Arctic convoys transported more than 4 million tonnes of supplies to the Soviet Union. More than 100 ships were lost with 3,000 sailors losing their lives.
To mark the 70th anniversary of the arrival of the first convoy in Russia - codenamed Operation Dervish - a group of British veterans travelled to Arkhangelsk.
At a ceremony by the River Dvina, I watched British and Russian war veterans embrace and take photographs of themselves together.
As a sign of their town's gratitude for Allied help in the war, local schoolchildren presented the UK visitors with red carnations.
A Russian boy with a remarkable voice performed a dramatic song about the perilous nature of the wartime convoys.
"When I left Russia at the age of 17 after my last convoy, I never dreamed that at the age of 85 I would still be coming back here," said merchant navy veteran Gordon Long MBE.
"We get such a wonderful welcome. We have so many friends here."
Among them is Russian war veteran Boris Grigorievich.
"I remember the convoys coming here. They arrived battered - they were all iced over - but they helped us so much and the main thing was that Russia and the Allies were working together," he said.
But there was a degree of suspicion, too.
A number of Russian women who fell in love with visiting British sailors were later arrested as spies and sent to labour camps, victims of Joseph Stalin's paranoia.
What is more, the headquarters of Capt Mond, chief of the British naval mission in Arkhangelsk, were reportedly bugged.
But UK veteran David Cottrell has no regrets for having been part of the operation.
"When we were on the convoys, we thought this was absolute hell," he admits.
"Looking back, I think this was one of the proudest moments of my life.
"My son tells me I must write all my memories down. 'You're living history,' he says. 'Once you're gone, it's all gone.'"
The British veterans' trip to Russia was funded by the Big Lottery Fund's Heroes Return 2 programme. The programme is open for applications until 31 January 2012. More details on how to apply are available via its advice line: 08454 10 20 30


Roedd goliau yn yr ail hanner gan Sean Morrison a Kenneth Zohore yn ddigon i gipio buddugoliaeth i Gaerdydd oddi cartref yn Leeds.

Mewn hanner cyntaf di-fflach fe aeth Greg Halford yn agos i Gaerdydd gyda pheniad o gic rydd Craig Noone, tra bod Allan McGregor wedi arbed cic rydd Chris Wood ar y pen arall.
Ar ôl 52 munud fe aeth yr Adar Gleision ar y blaen wrth i'r capten Morrison benio cic rydd Noone i gefn y rhwyd.
Dyblwyd y fantais gydag ugain munud i fynd wrth i Aron Gunnarsson greu cyfle i Zohore rwydo.
Cafodd Liam Bridcutt gerdyn coch hwyr i Leeds, wrth i Gaerdydd sicrhau tri phwynt gwerthfawr yn eu hymgais nhw i ddringo i hanner uchaf y tabl.


Five people involved in the Xinjiang attack that killed 31 people "blew themselves up", a Chinese report says.

The attack took place early on Thursday in a market place in Urumqi.
More than 90 other people were injured as attackers in two vehicles drove into crowds and threw explosives. One of the vehicles then blew up.
China called the attack a "violent terrorist incident", while the US called it an "outrageous act of violence against innocent civilians".
UN Secretary-General Ban Ki-moon said there was "no justification for the killing of civilians".
The latest information came from the state-run Global Times, which said it had "got information that five suspects who participated in the terrorist attack blew themselves up".
Police were investigating whether they had accomplices, the paper added. It was not clear whether the five were included in the death toll.
The BBC's John Sudworth, who is in Urumqi, said a heavy security presence had been deployed at the scene of the attack.
Some shops have opened again and there are a few signs of returning normality, but the shock over the brutality of what happened here remains, he says.
Why is there tension between China and the Uighurs?
With ranks of riot police now patrolling the area, local residents can be seen standing around, talking quietly to one another.
Some have friends and relatives who were killed or injured, run over by the cars that the attackers drove through the morning street market, or caught in the blast when one of the cars exploded, our correspondent adds.
Xinjiang, which is home to the Muslim Uighur minority, has seen a spate of attacks in recent years.
Beijing has blamed these - and other recent mass-casualty attacks - on Uighur separatists.
These include an attack in Beijing, where a car ploughed into pedestrians in Tiananmen Square, killing five people, and attacks at railway stations in Urumqi and Kunming.
China says it is pouring money into the Xinjiang region, but some Uighurs say their traditions and freedoms are being crushed.


Sale fly-half Dan Mugford missed a last-minute penalty as Newcastle held on to earn an opening-night win in the Premiership at Kingston Park.

With Sharks trailing by two points, Mugford sent the final kick of a low-quality game wide from the right.
Newcastle led 10-3 at the break after Sinoti Sinoti crossed in the corner.
Sale's Johnny Leota and Bryon McGuigan scored tries after the break, but Mike Delany's four penalties for Newcastle proved decisive.
Victory for Falcons, who finished 11th in the table last season, was their first in the opening game since 2007.
Neither side could get a grip on the game until Samoan wing Sinoti broke through Sale's defence to cross in the corner just before half-time.
Sale, without instrumental fly-half Danny Cipriani following his move to Wasps, finally came to life after the break, with Leota making a clever run to score.
Delany's accuracy with the boot extended the advantage to 19-10 before McGuigan ran in under the posts to make for a nervy final 10 minutes.
Replacement Mugford was given the chance to complete the comeback but could not find the target.
Newcastle: Hammersley; Goneva, Harris, Socino, Sinoti; Delany, Takulua; Welsh, Lawson, Vea, Green, Witty, Olmstead, Welch (capt), Wilson.
Replacements: Sowrey, Rogers, Lockwood, Fonua, Chick, Egerton, Hodgson, Waldouck.
Sale: McGuigan; Addison, James, Leota, Edwards; MacGinty, Phillips; Lewis-Roberts, Webber, Aulika, Evans, Ostrikov, Beaumont (capt), Ioane, Pearce.
Replacements: Briggs, Flynn, Longbottom, Mills, Lund, Seymour, Mitchell, Mugford.


Pupils in a primary school in Yorkshire will have to travel to another school for part of each day because of difficulties in recruiting a teacher.

Easington Primary Academy pupils will be driven to another school for morning lessons in literacy and numeracy.
The school said a long-term supply teacher had left earlier than expected and a replacement could not be found.
But a Department for Education spokeswoman said there was no shortage of primary school teachers.
Head teachers' organisations have been warning that a shortage of teachers has become a "crisis" for schools.
Brian Lightman, leader of the ASCL head teachers' union, said the problems facing this primary school were "symptomatic" of wider recruitment difficulties facing "head teachers all over the country".
"Urgent action needs to be taken to address this problem that is jeopardising efforts to raise standards," said Mr Lightman.
But a spokeswoman for the Department for Education said: "It is simply not true that there is a shortage of primary school teachers.
"Last year we recruited 116% of our primary target. However, we know that some schools, and particularly some rural schools, find it more difficult to recruit."
She said that the government was expanding routes into teaching such as Teach First and had launched the National Teaching Service to  "send outstanding teachers into areas exactly like this".
"We expect head teachers and academy trusts to plan their staffing properly," said the DFE spokeswoman.
From this term, because the school could not find a suitable teacher, pupils in Years 5 and 6 at Easington will have to travel to Patrington Primary Academy for the morning, returning to their own school after lunch.
Patrington and Easington are part of the same academy trust and share an executive head teacher.
A statement from the trust said:
"A great deal of thought has gone into how the academy can best meet the needs of the pupils, especially for Year 6 pupils who will be taking Sats [national curriculum tests] in May," said the William Temple Academy Trust.
"We recognise that this means more change for the Easington Years 5 and 6, but we have no option.
"We hope that being taught by the class teachers at Patrington will provide more consistency for the pupils than a succession of supply teachers for a couple of weeks at a time."
A meeting for parents to discuss how the arrangement is working is planned for later this month.
Labour's shadow education secretary Lucy Powell said: "Whilst ministers continue to bury their heads in the sand over teacher shortages, we are seeing more and more evidence that this serious issue is threatening standards."
Ms Powell accused the government of denying there was a problem with recruitment, "despite the fact that half of all schools had unfilled positions at the start of this academic year and some pupils are now having to travel to other schools for their maths and English lessons".
National Union of Teachers' leader Christine Blower said recruitment problems were "of the government's own making" and warned that they could get worse.
"Failure to address excessive and often pointless workload alongside low and unpredictable pay have resulted in a huge number of teachers considering leaving  the profession while new graduates are choosing other more attractive career options."
Last month, head teachers warned MPs on the Education Select Committee of a deepening "crisis" in recruiting and retaining teachers.
The National Association of Head Teachers said 59% of schools advertising for teachers "struggled" to get applicants and a further 20% failed completely to appoint anyone.
Teachers' recruitment expert Prof John Howson told the MPs the current teacher shortage was the worst since 2001-02.


Sam Griner has gone from success kid to success kidney.

As a toddler, Sam was snapped on a beach with a determined expression and one fist clenched - an image that spawned the well-known "success kid" meme.
The image has been used widely online by people seeking to celebrate happy moments, small victories and good days.
Now eight, Sam's net fame is being used to raise cash for a kidney transplant for his father.
Sam's father Justin fell ill in 2006 and suffered total kidney failure in 2009. He has been on dialysis ever since. Mr Griner's mother died from the same disease.
In a week, the fund-raising campaign has won pledges of more than $93,000 (Â£63,000) - far more than the $75,000 needed to pay for the medical procedure.
Health insurance is covering some of the costs of Mr Griner's treatment but the family needs extra cash to pay for the operation and care to help him recover afterwards.
The Griner family are also using the fund-raising page to look for people who are a good tissue match and willing to donate a kidney.
In an interview with the Daily Dot, Sam's mother said a transplant was the only way to save her husband's life.
Ms Griner said she was initially sceptical about using her son's internet fame to raise money but realised it could be a good way to highlight the cause.
"We're the parents of 'Success Kid' for goodness' sake," Ms Griner told the news site. "If anyone understands the power, the mass, and goodwill of the internet, it's those of us lucky to experience it daily."
Other net famous people have also used their appearance in memes to raise cash for good causes. Laina Morris, better known as the face of the overly-attached girlfriend meme, has used her YouTube channel to highlight charities needing cash.


More than 70 Republicans have signed a letter to the party's National Committee head urging him to stop helping Donald Trump's campaign.

They said Mr Trump's "divisiveness" and "incompetence" risked drowning the party in November's election.
The letter said that the party should instead focus on protecting vulnerable candidates in elections to the Senate and the House of Representatives.
Former members of Congress are among the signatories of the letter.
"We believe that Donald Trump's divisiveness, recklessness, incompetence, and record-breaking unpopularity risk turning this election into a Democratic landslide," said a draft of the letter obtained by Politico.
"Only the immediate shift of all available RNC (Republican National Convention) resources to vulnerable Senate and House races will prevent the GOP from drowning with a Trump-emblazoned anchor around its neck."
The letter added: "This should not be a difficult decision, as Donald Trump's chances of being elected president are evaporating by the day."
Reacting to the move, Mr Trump said he was not concerned that the party could cut him off.
"All I have to do is stop funding the Republican Party," the billionaire said.
Time Magazine on Thursday reported that RNC Chairman Reince Priebus had threatened to withdraw funding from the Trump campaign, and instead direct it to Congressional campaigns.
Mr Trump denies that this conversation ever took place.
The Republican presidential nominee has endured 10 days of negative headlines after a string of controversial comments.
In recent weeks, several leading Republicans have deserted Mr Trump over his outspoken attacks.
Polls suggest support for the embattled candidate has been falling in key battleground states in recent weeks.


A look at the best supporting actress nominees for the 88th Academy Awards, announced on 14 January 2016.

JENNIFER JASON LEIGH
Age: 53
Nominated for: The Hateful Eight
The character: Daisy Domergue, an outlaw awaiting execution in 19th Century Wyoming.
Oscar record: No previous nominations.
The critics said: "The best part of The Hateful Eight is Leigh, who brings mischievous grit to her every appearance." [Montreal Gazette]
ROONEY MARA
Age: 30
Nominated for: Carol
The character: Therese Belivet, a shopgirl and aspiring photographer in 1950s New York who begins an affair with a glamorous older woman.
Oscar record: Best actress nomination for The Girl with the Dragon Tattoo in 2012.
The critics said: "There are obvious asymmetries to be discovered in the relationship between a penniless young bohemian and a wealthy, full-grown matron, but Ms Mara refuses to be the ingenue in the arrangement. She is vulnerable and hungry, timid and ferocious, predator and prey." [New York Times]
RACHEL McADAMS
Age: 37
Nominated for: Spotlight
The character: Sacha Pfeiffer, an investigative reporters at the Boston Globe who helps uncover child abuse in the Catholic Church.
Oscar record: No previous nominations.
The critics said: "Rachel McAdams brings her typical resolute intelligence to Sacha Pfeiffer... whether quietly interviewing abuse victims or caught off guard coming face to face with one of the accused priests, she's entirely human and it's telling how often McCarthy chooses to resolve a scene on a look from her." [IndieWire]
ALICIA VIKANDER
Age: 27
Nominated for: The Danish Girl
The character: Artist Gerda Wegener, whose husband became Lili Elbe, the Danish artist and transgender pioneer.
Oscar record: No previous nominations.
The critics said: "How Gerda copes... is even more gripping. She proves astonishingly supportive towards her partner's plight. Vikander eats this all up with a spoon, by turns energetic, winning, raw and compassionate... it seems she can do anything." [Empire]
KATE WINSLET
Age: 40
Nominated for: Steve Jobs
The character: Joanna Hoffman, loyal assistant to Apple co-founder and tech pioneer Steve Jobs.
Oscar record: Won best actress for The Reader in 2009. Three best actress nominations for Titanic in 1998, Eternal Sunshine of the Spotless Mind in 2005 and Little Children in 2007. Best supporting actress nomination for Sense and Sensibility in 1996 and Iris in 2002.
The critics said: "Don't be surprised if Kate Winslet also gets a nod in the best supporting actress category for her part as Jobs's right-hand-woman." [Evening Standard]


A trade union has said 30 workers have been made redundant at the Shivo factory in Londonderry.

The aerospace engineering firm, formerly known as Maydown Precision Engineering, went into administration earlier this month.
The other 50 staff are due to return to the factory floor on Wednesday afternoon.
Liam Gallagher from the Unite union said their future is still uncertain.
"Thirty workers will be made redundant and unfortunately those workers will have to seek that statutory redundancy," he said.
"The other workers will be returning to work this afternoon to fulfil outstanding contracts and obviously we are deeply concerned about the prospects for those workers.
"Obviously there is absolutely no guarantee beyond the existing contracts that are there."
Administrators were called into Schivo NI, formerly known as Maydown Precision Engineering (MPE), a supplier to major aircraft manufacturers such as Bombardier.
MPE was bought by the Waterford-based Schivo Group two years ago.
A spokesperson for the company said the group had been "unable to turn around Schivo NI Ltd".
In August 2015, the workers union, Unite, voiced concerns over possible job losses.
The company had previously said it would be expanding its interests in the aerospace engineering sector.
The Schivo Group has business interests in the medical technologies, aerospace and oil and gas sectors.