President Anwar Sadat of Egypt today urged Israeli Prime Minister Menachem Begin to join him in a new summit conference to rescue the stalled Palestinian autonomy talks after the U.S. presidential election.

The proposal, in a 35-page letter to Begin delivered today, would, in effect, put the faltering talks on hold until that little can be accomplished until President Carter is either reelected to office -- and thus freed from the need for Jewish electoral support -- or replaced by one of his rivals who will make a fresh start in the Middle East negotiations.

If it is accepted by Begin and Carter, Sadat's suggestion will allow a long pause while the United States is absorbed by the elections. The delay averts the embarrassment to Carter of a visible failure in the Camp David process, which has been his largest single claim to foreign policy success.

[A State Department spokesman said the U.S. government supported "whichever method offers the best prospects" for resuming the suspended Egyptian-Israeli talks, but did not take a position immediately on the Sadat proposal. Spokesman David Passage said Carter's special Middle East envoy, Sol Linowitz, was planning a trip to Cairo and Jerusalem in late August or early September to discuss ways of resuming the talks.]

Although he did not specifically say so, Sadat appeared to have in mind a three-way summit with Carter, along the lines of the Camp David meetings in September of 1978 that produced the Egyptian-Israeli peace accords. Since Sadat's trip to Jerusalem in November 1977, he and Begin have met nine times but have produced substantial breakthroughs only during the extended Camp David sessions, when Carter took the leading role.

In what seemed to be an indirect threat that the entire Camp David process could be endangered unless some agreement is reached when another summit is finally held, Sadat said:

"If the generous offers I make for the sake of peace are neither appreciated nor acted upon, we will have to start with a clean slate, but we will not be deterred in our holy search for peace and justice for all peoples of the area."

Observers noted that this marked the first time Sadat has raised -- even indirectly -- the possibility that some other form of peace talks might replace the Camp David framework put forward by the Carter administration as the only course offering any hope of progress.

After long, familiar arguments disputing Begin's contentions on why the talks are stalled, Sadat charged that the Israeli leader has failed to respond to Egypt's reasons for suspending negotiations Aug. 3 for the second time since they began 15 months ago.

The chief Egyptian objections are Begin's policy of continued Jewish settlements on the Israeli occupied West Bank and a recent Israeli law asserting that Jerusalem, including the Arab eastern section captured from Jordan in 1967, is Israel's permanent capital. Since Sadat halted the talks, Begin has reaffirmed his refusal to change either of these stands in the negotiations.

"Thus the obstacles on the road to peace remain there," Sadat wrote, and I can not see how we can resume the negotiations under these circumstances."

Given the seemingly irreconcilable discord between the two positions, the Egyptian leader said, "I believe the best course of action for us is to hold a summit conference in an attempt to stem these lingering differences before they jeopardize our mission."

Then, in an ostentatious salute to Carter, he added:

"On the other hand, it would be unfair and discourteous to impose this problem on our friend and full partner President Carter at this point in view of his other preoccupations, which are obviously more pressing.

"You remember that I described him at Camp David as the unknown soldier who dedicated himself to the cause of peace. The least we can do in recognition of his contribution is to appreciate his position and hold the summit when these preoccupations are over. I am sure that you share this view with me."

Egyptian officials have made no secret of their desire to see Carter reelected. In their view, he would be free in his second term to put increased pressure on Israel for concessions in the talks, designed to set up self-rule for the West Bank and Gaza.

Some Israeli political figures and a large part of Israeli public opinion also share this expectation, one that evokes fear in Israel though not in Egypt. Thus, if Sadat's idea is embraced and the talks are suspended, the top diplomatic goals of Egypt and Israel will be at stake to an unusal degree in the American presidential election outcome.

At the same time, Sadat's suggestion would present other advantages for Egypt. Foreign Ministry officials here have been watching with keen interest the growth of a unified Arab stand against the July 30 law declaring all Jerusalem to be Israel's eternal capital. A pause would give this current time to build.

The officials gave particular attention to Wednesday's statement by Crown Prince Fahd of Saudi Arabia suggesting that Israel's actions on Jerusalem proved the Camp David negotiations have failed. Egypt remains committed to the talks, they said.

In his letter to Begin, Sadat referred at length to his need to take such Arab sentiment into account. Some reports have suggested that the Saudis are encouraging Sadat's strong stand on Jerusalem in hopes of ending, or at least softening, the bitter quarrel that has divided the Arab world since the Egyptian-Israeli peace treaty was signed in March of 1979.