By Sabine Siebold and Mike Stone

BERLIN/WASHINGTON, Feb 18 (Reuters) - Germany is considering ordering more U.S.-made F-35 fighter jets, two sources told Reuters, a move that would deepen Berlin's reliance on American military technology as its joint next-generation fighter program with France falters.

One source said Berlin was in negotiations that could lead to the purchase of over 35 additional jets. Germany purchased 35 of the aircraft in 2022 which are due to begin delivery later this year.

The potential acquisition of more Lockheed Martin LMT.N stealth fighters, at a cost of more than $80 million per plane, would follow pressure from Washington on European allies to increase defence spending.

If all the potential F-35 purchases and existing orders come to fruition, Germany would have around 85 F-35s. But the sources cautioned the outcome was still uncertain.

Germany's Defence Ministry did not immediately comment while a Pentagon spokesperson referred questions to Germany. A spokesperson for defence contractor Lockheed Martin LMT.N said the company was focused on building F-35s already ordered by Germany.

In October, a German parliamentary source said the defence minister intended to order 15 more F-35s. Germany was expected to announce that purchase in the near-term, the second source said.

Expansion of Germany's F-35 fleet would mark a significant strategic shift toward deeper military integration with the United States and away from European defence autonomy, a priority for fellow European Union member France.

Germany and France are deadlocked on their Future Combat Air System (FCAS) program, a problem-plagued, 100-billion-euro effort launched in 2017 to build a next-generation aircraft to replace French, and German and Spanish jets starting in 2040. Under the emerging scenario, Germany and France would abandon the FCAS project.

A commitment by Germany to add F-35s to its arsenal would also have implications for NATO as the jet plays a key role in the alliance's nuclear strategy.

Buying more F-35 jets would give Germany time to figure out developing and finding a partner for a jet project.

German Chancellor Friedrich Merz on Wednesday questioned whether developing a manned sixth-generation fighter jet, as FCAS has sought to do, still made sense for his country's air force.

"Will we still need a manned fighter jet in 20 years' time? Do we still need it, given that we will have to develop it at great expense?" Merz said on the Machtwechsel podcast published on Wednesday.

Berlin's 2022 decision to buy the U.S.-made F-35 was driven by its NATO obligation to deliver U.S. nuclear bombs stored in Germany if called upon. The F-35 is the only Western fighter jet certified to carry the most modern B61 nuclear bombs and is central to replacing Germany's aging Tornado jets, which play that role now.

While insiders expect Germany and France to abandon a joint fighter jet, they anticipate the allies will continue to cooperate on drones and digital warfare infrastructure.

German Defence Minister Boris Pistorius said last week the fate of FCAS would become clear within days.

(Reporting by Mike Stone in Washington and Sabine Siebold in Berlin; Editing by Chris Sanders and Cynthia Osterman)

((mike.stone@thomsonreuters.com;))