Mayor Sharon Pratt Dixon, in an apparent reversal of an earlier position, will not ask for the resignations of the trustees of the University of the District of Columbia, several of the trustees said last night.

Instead, Dixon will quickly add "new blood" to the board by filling three vacancies, said Paul Costello, a Dixon spokesman. He said any changes beyond filling those vacancies on the 15-member board will not occur until after trustees select a new university president.

Dixon's decision came after an hourlong meeting yesterday between Dixon and the trustees, the first since the mayor told reporters and editors of The Washington Post in an interview two weeks ago that she would prefer to have new trustees on UDC's board.

Trustees described the meeting with Dixon as cordial and constructive. Several had been angered by reports that Dixon was planning to ask for their resignations without having first talked with them, and some had threatened to resign immediately.

Such a move would have made it difficult to hire a new president. Trustees have set May as the tentative deadline for the selection.

A mass resignation also could have jeopardized the university's accreditation, which is being reviewed by a regional accrediting agency.

"The mayor never intended to seek resignations," Costello said after the meeting last night. "She gives her full commitment to the board, and she plans to work with the board to phase in new blood."

Still, Costello said Dixon's intention for change on the board "goes beyond the three vacancies." He declined to elaborate.

Trustees interviewed after the meeting said that Dixon's apparent change of mind appeared to be a case of "growing pains" in a new administration. "I think it was that her staff is still getting to know her and how she thinks," one said.

UDC trustees serve for five years and can be removed only for cause, and only by the D.C. Council. Eleven members of the 15-person board are appointed by the mayor or the council, and three of those appointed positions are vacant. Three trustees are elected by alumni and one by students.

However, legislation pending before the council could change the length of the trustees' terms and the size of the board. Currently, about half of the trustees' terms expire in May 1993, the other half in May 1994.