* Deal could strengthen Lockheed's position in European tenders
* Belgian order estimated to be worth more than $4 bln
* F-35 deal would represent blow for Eurofighter project (Adds context, Lockheed comment)
By Philip Blenkinsop and Andrea Shalal
BRUSSELS/BERLIN, Oct 22 (Reuters) - Belgium has chosen Lockheed Martin's F-35 stealth jets over the Eurofighter Typhoon to replace its ageing F-16s, news agency Belga cited government sources as saying, in a move that would cement the U.S.-made war plane's position in Europe.
The country has been deliberating for months over a multibillion-dollar purchase of 34 new fighter jets, with the latest deadline for a decision being Oct. 29.
A defence ministry spokeswoman declined to comment on the government's decision and did not confirm the end-October deadline.
Lockheed spokeswoman Carolyn Nelson did not confirm that a decision had been made but said the company remains confident that the F-35 is the right choice for Belgium.
"The F-35 offers transformational capability for the Belgian Air Force and, if selected, will align them with a global coalition operating the world's most advanced aircraft."
If confirmed, the decision will make Belgium the 12th country to buy the radar-evading F-35 jets and could help to strengthen the U.S. aerospace company's position in forthcoming tenders in Switzerland, Finland and Germany.
The decision, the likely outcome of which was reported by Reuters last Friday, had been expected in July before the NATO summit in Brussels. The order for jets due for delivery from 2023 is estimated to be worth 3.6 billion euros ($4.14 billion).
Washington has extended the terms of the F-35 bid to Oct. 31 at Brussels' request, U.S. sources said, adding that any further delay would trigger changes in pricing.
Lockheed has said its bid will give Belgian companies significant opportunities to contribute to the global F-35 enterprise.
Belgian Prime Minister Charles Michel has previously said he would like to make the decision on the F-16 replacements before a national election in May and Defence Minister Steven Vandeput has said he hoped to settle the matter before he steps down at the end of the year.
A win for Lockheed would mark a setback for Britain, Germany, Italy and Spain, the four countries behind the Eurofighter programme, who had mounted a strong lobbying campaign for the European war plane.
It is also likely to anger France, which did not submit a formal bid for the Rafale fighter built by Dassault Aviation but had offered Belgium close defence cooperation to prevent a further spread of the F-35 in Europe.
Other European buyers of the F-35 include Britain, the Netherlands, Denmark, Italy, Turkey and Norway.
The Eurofighter is flown by Germany, Britain, Austria, Italy and Spain. ($1 = 0.8692 euros) (Reporting by Philip Blenkinsop in Brussels and Andrea Shalal in Berlin Editing by Alastair Macdonald and David Goodman)