U.S. ambassador to Egypt and Israel were flying back to Washington last night for a weekend review of the suddenly endangered negotiations on Palestinian autonomy.

State Department sources said Secretary of State Edmund S. Muskie and special Middle East negotiator Sol M. Linowitz will participate in the sessions.

The planned meetings were called a policy review rather than "a reassessment," a word with more threatening connotation because of its use by former secretary of state Henry A. Kissinger during periods of tension with Israel in the negotiations after the 1973 Middle East war.

U.S. officials took a serious but not alarmed view of the unexpected decision by Egyptian President Anwar Sadat to postpone further ministerial-level negotiations with Israel about autonomy for the 1.2 million Palestinians living in the West Bank and Gaza.

Sadat's decision was interpreted as his way of administering a jolt to the Israeli leadership, which in his view has been showing insufficient flexibility in the autonomy negotiations, the next step in the Camp David peace process.

Officials noted that Sadat has not ceased all contact or withdrawn his negotiating team as he did during a period of frustration with Israel in January 1978. The expectation this time is that Sadat will return to the bargaining table after making clear through the interruption that he is displeased with the progress of the talks.

The weekend meetings will be Muskie's first opportunity for thorough discussions of the Middle East problem, which consumed so much of the time of his immediate predecessors, Kissinger and Cyrus R. Vance. It will also be his first chance for lengthy talks with the two U.S. envoys, Alfred L. Atherton (Egypt) and Samuel W. Lewis (Israel).

The slow pace of progress in the recent talks has made it highly unlikely that they can be concluded by the May 26 target date, and it is uncertain how much progress toward concrete agreements can be shown by that date, officials conceded.

The United States is expected to do all it can to prevent a collapse of the talks, which would bring a halt to the Palestinian side of the Camp David process, threaten the peace position of Sadat and have major repercussions throughout the Middle East.

In Washington's effort, revision is expected to concentrate on maintaining enough progress in the talks to keep them alive as a credible process, even if the sensitive and to some extent technical issues involved are not completely solved.

The U.S. position as Mideast negotiator -- plus the recent furor over a "mistaken" U.S. vote March 1 regarding Israeli settlements in the occupied West Bank -- contributed to the U.S. decision to abstain from voting on an Arab-backed resolution in the Security Council last Thursday.

President Carter's campaign for reelection makes U.N. votes against Israel or pressures on Israel more difficult, sources said.

Thursday's U.N. resolution, which was supported by all 14 other members of the Security Council, called on Israel to undo the "illegal" deportation of three West Bank Arab leaders.

The Arab sponsors had watered down the language of the resolution to meet objections of the United States, which had criticized the deportations in a State Department statement last Tuesday.