UPDATE 1-Pentagon eyes F-35 sales to Greece, Romania and Poland -U.S. official

(Adds background)

By Mike Stone

WASHINGTON, April 4 (Reuters) - The United States is considering expanding sales of Lockheed Martin Corp-made F-35 fighter jets to five new nations including Romania, Greece and Poland as European allies bulk up their defenses in the face of a strengthening Russia, a Pentagon official told Congress on Thursday.

In written testimony submitted to the U.S. House of Representatives and seen by Reuters, Vice Admiral Mathias Winter - the head of the Pentagon's F-35 office - said that "future potential Foreign Military Sales customers include Singapore, Greece, Romania, Spain and Poland."

Other U.S. allies have been eyeing a purchase of the stealthy jet including Finland, Switzerland and the United Arab Emirates.

Winter's testimony said the United States would respond to all official requests for information about the jet.

Last year, Belgium said it chose the F-35 over the Eurofighter Typhoon to replace its ageing F-16s in a 4 billion euro ($4.55 billion) deal.

Germany has knocked the F-35 out of a jet fighter competition worth billions of euros.

Last year, the United States rolled out a new "Buy American" plan that relaxed restrictions on sales while encouraging U.S. officials to take a bigger role in increasing business overseas for the U.S. weapons industry. (Reporting by Mike Stone in Washington Editing by James Dalgleish)