Germany has urged the UK to stick to its commitments
The UK is under growing pressure over the Eurofighter defence programme amid reports it wants to renegotiate the cost of a £1.4bn contract.
Government sources say Gordon Brown spoke to German Chancellor Angela Merkel about the issue this week as negotiations over its cost drag on.
The UK is prepared to buy 16 combat planes from the European consortium but is understood to want to pay less.
Germany and other European partners want a speedy outcome to negotiations.
Value for money
The German, Italian and Spanish governments are concerned that vacillation by the UK could endanger the future of the project and put jobs at risk.
But the UK is seeking greater value for money from the latest phase of the Eurofighter project as constraints on its defence budget increase.
The four countries - which launched the Eurofighter programme in 1988 - have been in talks over sharing 112 combat jets between them in a deal worth more than £100bn.
The UK has committed to ordering 16 for its own use.
Under the original agreement, the four countries were to split 620 jets between them in three separate batches.
The BBC's political correspondent Iain Watson said there is tension over the negotiations with sources suggesting the UK is determined to bear down on costs while its partners were more worried about securing the future of 100,000 jobs.
Manufacturers of the jet fighter, including UK defence firm BAE Systems, have warned of thousands of job losses from 2012 onwards if no agreement is reached.
However, it is thought the talks, which have been going on for months - are advanced and the likelihood of the orders being cancelled is slim.
The global recession is forcing all countries to reconsider their defence budgets.
With an estimated cost per plane of £100m, the Eurofighter programme has come under particular scrutiny.
The Royal Air Force (RAF) took delivery of its first quota of Eurofighter Typhoon jets in 2003.
Last year it declared the Typhoon capable of carrying out ground attacks in addition to its original air defence role.
Critics say the Typhoon is an outdated Cold War weapon, unsuitable for modern wars against terrorists and insurgents.
But the RAF says the upgrade means the fighter will be able to operate more effectively in Iraq and Afghanistan.