UPDATE 1-Belgium chooses Lockheed's F-35 to replace F-16 jets -Belga

(Adds order detail, decision deadline)

BRUSSELS, Oct 22 (Reuters) - Belgium has chosen Lockheed-Martin's F-35 jets rather than the Eurofighter Typhoon as a replacement for its ageing F-16s, Belgian national news agency Belga said, citing government sources.

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.

The decision, eagerly awaited by the aerospace industry, 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.

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. 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 U.S. aerospace company Lockheed would mark a setback for Britain, Germany, Italy and Spain, the four countries behind the Eurofighter programme. ($1 = 0.8692 euros)

(Reporting by Philip Blenkinsop Editing by Alastair Macdonald and David Goodman)