Assistant Secretary of State Elliott Abrams, citing a scheduling conflict, did not appear yesterday before a House panel where he would have been put under oath by a Democratic chairman who questions his veracity.

Abrams, under fire in the Iran-contra affair, sent Deputy Assistant Secretary of State for Inter-American Affairs Richard N. Holwill to testify about the situation in Panama before the House Foreign Affairs subcommittee on Western Hemisphere affairs. Aides cited a "scheduling conflict" because Abrams was meeting with Costa Rican President Oscar Arias, in Washington on a private visit.

An Abrams aide said the panel was told last week that an Abrams appearance yesterday could only be tentative because of the possibility that other commitments would take precedence. The aide said the staff was told Abrams might not appear.

But congressional aides said the panel was notified an hour before the hearing that Holwill would testify instead.

Rep. George W. Crockett Jr. (D-Mich.), chairman of the House subcommittee, said he was "as surprised as everyone else" when Abrams failed to appear, although he said he leaves it to the staff to schedule witnesses.

Abrams, assistant secretary of state for inter-American affairs, is under intense criticism on Capitol Hill for misleading Congress about government involvement in aiding the Nicaraguan contras while official U.S. assistance was banned.

A number of lawmakers have accused Abrams of lying to Congress and urged him to resign.