President-elect Ronald Regan has selected David M. Abshire, chairman of Georgetown University's Center for Strategic and International Studies, for a key supervisory role over foreign policy and defense aspects of the presidential transition, informed sources said yesterday.

Abshire, 54, was assistant secretary of state for congressional relations during three years of the Nixon administration. After leaving the government to return to the Georgetown Center, which he helped establish, he also served as chairman of the U.S. Board for International Broadcasting and as a member of the Congressional Commission on Organization of the Government for Conduct of Foreign Policy.

Abshire's role, according to the sources, will be to supervise a cluster of transitional teams for government departments, including the State Department, Defense Department and Central Intelligence Agency. His appointment and those of the department team members are to be announced early this week by the Reagan staff.

It was unclear yesterday how much authority Abshire will wield over the cluster of departmental teams. However this turns out, his selection was considered significant as another indication that Reagan will turn for advice to experienced persons within the mainstream of foreign and defense ideas.

Abshire took no part in the Reagan campaign, but his Georgetown Center supplied so many members of Reagan advisory committees that there was good-natured speculation in Washington that the place will be deserted after Inauguration Day.

There was renewed speculation yesterday that the most illustrious of the Georgetown Center's personnel, former secretary of state Henry A. Kissinger, might be offered that job in the Reagan administration.

Reagan, in a Time magazine interview granted just before the election, seemed to rule this out by saying that Kissinger "has made it very plain that he does not want to be a part of the administration," but would be available for special missions. In a press conference Thursday, Reagan refused specific comment on the possibility of Kissinger becoming his secretary of state.

Kissinger, who was in New Orleans Friday for a Georgetown Center conference on the Caribbean, was quoted by United Press International as declining to say whether he would agree to resume his old job as secretary of state if it were offered. "It would be arrogant in the extreme to say I will not under any circumstances respond to what the president might ask of me when he hasn't even asked," Kissinger was quoted as saying. He did, however, rule himself out as a future presidential assistant for national security affairs, another job he has held before.