Secretary of State Cyrus R. Vance will fly to the Middle East this weekend in an effort to avoid a complete breakdown of the eight-month-old Egyptian-Israeli peace initiative, administration officials said yesterday.

Fears of a total collapse of the effort, which grew out of Egyptian President Anwar Sadat's dramatic visit to Israel last year, were sparked over the weekend by Sadat's public rejection of new talks with the Israelis and by equally uncompromising private messages he sent to Washington.

In the strongest criticism it has issued of him since the Jerusalem visit, the State Department issued a statement yesterday saying it was "very disappointed that President Sadat will not participate in another round of negotiations with Israel under present circumstances."

The statement, read to reporters by spokesman Hodding Carter, was telephoned from Camp David, Md., where Vance met with President Carter, Vice President Mondale and other foreign policy advisers. The meeting had been scheduled before Sadat's rejection of new contacts, but reportedly was largely devoted to the Middle East.

As late as Friday, planning for Vance's trip continued to center on hopes of getting the Egyptian and Israeli foreign ministers together for talks in the Sinai desert. Vance indicated after meeting with the two ministers in Leeds Castle in England July 19 that the three would meet again jointly and that the talks might be expanded to include the defense ministers and military experts of the two nations.

By last night, however, such hopes had virtually disappeared. A State Department official said that Vance now expects to spend no more than five days on the trip, arriving in Jerusalem late Saturday and traveling to Alexandria on Monday before returning to the United States.

But Sadat's statement Sunday "raises a new set of circumstances which we do believe requires close consultation," Hodding Carter said at the daily State Department briefing.

Thus far the United States is not prepared to use the trip to present an American peace plan, a State Department official said. Sadat suggested Sunday that such a move was needed to break the deadlock, which the Egyptian leader attributed to Israeli statements last week that the Arabs would have to give up some of the lands lost in the 1967 war if there is to be final peace agreement.

In Jerusalem, Israeli Prime Minister Menachem Begin expressed satisfaction over the State Department's criticism of Sadat's position, telling reporters that it was "about time the world began to understand who the truly intransigent party was."

Pessimism appeared to be deepening in Jerusalem as well as Washington. In a presentation to a parliamentary committee, Israeli Foreign Minister Moshe Dayan quoted the State Department's special Middle East envoy, Alfred Atherton, as saying Saudi Arabia believed the Israeli-Egyptian negotiations had reached the end of the road.

Saudi Arabia's prime minister, Crown Prince Fahd, left Alexandria yesterday after two days of talks with Sadat. He now moves to Damascus for talks with Syrian President Hafez Assad, who has joined other "hard-line" Arab states in opposing the Sadat initiative. Arab foreign ministers met in Belgrade last week and a noticeable hardening of Arab attitudes appears to have followed.

Vance had said that he would not undertake a new trip to the Middle East unless it involved direct negotiations between the Israeli and Egyptian foreign ministers. He had originally intended to follow stops in Egypt and Israel with the three-party meeting at an American-manned monitoring station in the Sinai desert, and to visit Saudi Arabia and Jordan before returning home.

There was discussion of canceling Vance's journey within the administration, according to one official, who reported that the decision to go ahead with a trip that promises no progress was made at Camp David yesterday.