An ambitious bid to examine American policy during the war in Vietnam in being launched by Rep. Lester L. Wolff (D-N.Y.), chairman of the House International Relations Subcommittee on Asian and Pacific Affairs.

Since the emergency evacuation of the last American officials from Saigon as North Vietnam seized control of South Vietnam in April, 1975, the war record has been deliberately avoided in Congress. The Ford administration then in power, opposed any inquiry by itself or by Congress, on grounds of sparing the nation further trauma or recrimination.

"I don't think we can dig our heads in the sand any longer," Wolff said yesterday. With the United States now attempting to normalize relations with the Communist victor, Wolffsaid, "it is time to examine what really happened in Vietnam.

Wolff, whos is 58, and lists in his congressional biography 12 years' experience as a "television moderator and producer," acknowledged yesterday that "It's kind of a monumental task."

His interest in reopening the record on Vietnam was whetted by the inquiry about the originally secret letter from then president Nixon to North Vietnamese Premier Pham Van Dong in 1973. That dispute brought former Secretary of State Henry A. Kissinger before the Wolff subcommittee on Tuesday. Kissinger denied, as Nixon had, that the letter represented any "unconditional committment" to give postwar aid to North Vietnam.

Although several Republican subcommittee members said that should end that dispute, Wolff said yesterday that "I've been given authority by the chairman of the full committee for all matters relating to Vietnam."

He said. "My subcommittee will have to go back and really examine some of the elements that took place," in the conduct of the war and the diplomacy surrounding it, "in order to make a determination of what our position should be" in the future.

A newer generation, Wolff said, is asking. "How did we get involved? Was there profiteering in the war? What really happened [in 1964] in the Gulf of Tonkin?" The information disclosed in the 1971 Pentagon Papers on Vietnam, Wolff said, did not go deep enough to answer all the questions.

Wolff said that he has informally explored a broad Vietnam inquiry with many subcommittee members and plans a formal discussion next week. His subcommittee only has a staff of four, he said. But Wolff said that can be enough for a study to examine the cost and scope of an inquiry that would be "totally impartial, non-political," reaching back to "the Kennedy days, the Johnson days," in order "to get the facts straight."