Britons are disputing a claim by former Navy Secretary John Lehman that Britain would have lost the 1982 Falklands War without extensive American military aid.

Lehman disclosed in an interview with the British Broadcasting Corp. that the United States provided crucial military aid to London during the 1982 Falklands War and said Britain would have lost without it."Britain would have had to have withdrawn from the Falklands" if the United States had cut off the aid, Lehman, Navy secretary from 1981 to 1987, said in the interview to be broadcast Wednesday as part of "An Ocean Apart," a BBC television documentary series on Anglo-American relations.

The Observer, the London newspaper that first revealed the contents of the interview in Sunday's editions, said Lehman's remarks "are certain to stir up resentment" in Britain before President Reagan's visit Thursday from his summit talks with Soviet leader Mikhail Gorbachev.

Member of Parliament Michael Mates, chairman of the House of Commons Defense Select Committee, told The Observer: "If Mr. Lehman is saying we couldn't have won without the Americans, he is wrong. It would have taken longer, cost more lives and been much more difficult - but we could still have done it."

Britain defeated Argentine invasion forces in a 74-day war in 1982 to regain control of the Falkland Islands, about 450 miles off Argentina's coast in the South Atlantic. The islands, which the Argentines call Las Malvinas, have been under British rule for more than 150 years.

Although it was known that Britain had some U.S. help, including use of the American air base on Ascension Island in the central Atlantic, the extent of U.S. military aid during the Falklands war has been a secret. Lehman is the first senior U.S. official to state that the Pentagon's supplies were so great as to have been decisive.