President Carter, assessing his separate talks with Israeli Prime Minister Menachem Begin and Egyptian President Anwar Sadat, said yesterday that the problems impeding agreement on Palestinian self-rule are "much less formidable" than those of earlier stages in the Mideast peace process.

But the optimism Carter expressed at a White House ceremony and in a nationally televised news conference was offset by Begin, who gave a hardline speech here warning that Israel is unwilling to make compromises in its negotiating position.

Following his two days of talks with Carter, Begin told American-Jewish leaders that Israel never will agree to an autonomy scheme for Israeli-occupied Arab lands if it means "a Palestinian state in name or a Palestinian state in everyting but name."

Begin, who spoke at the Shoreham American Hotel before leaving Washington, said he had been asked, apparently by the White House, to postpone a response to Sadat's suggestion that Palestinian residents of East-Jerusalem be given a degree of local autonomy and be allowed to vote in the self-governing process for the West Bank and Gaza Strip.

"I had to reply on the spot," Begin said. "Without any qualification, the world should know -- all nations -- that on this issue Jerusalem is D.C. -- like the District of Columbia, D.C. -- David's Capital.

"May I now respond to all of these proposals," he added. "Jerusalem -- East, West, North, South -- all of it is under one sovereignty, that of Israel."

He repeated that Israel is willing to allow limited, local self-government for the 1.2 million Palestinians in the West Bank and Gaza. But he rejected the idea that any self-governing authority should have the powers of a legislative assembly or other characteristics that might form the nucleus of an independent Palestinian state.

A Palestinian state, he said, "would be a mortal danger to us. It would hold hostage every city and town in Israel." He added that guarding against this danger means continuing to establish Jewish settlements in the occupied territories.

"They are settlements to which we have an eternal and inherent right, and we shall not give up that right," Begin warned.

His emotional restatement of the Israeli position made clear that Carter's talks over the past two weeks, although successful in resolving some procedural problems, did not make any progress in bridging the gap between the Israeli and Egyptian approaches to Palestinian autonomy.

The separate meetings with Sadat and Begin did achieve agreement for an intensified new round of negotiations before the May 26 target date for an autonomy accord. They also produced a potentially significant agreement that some aspects of the autonomy accord could be bucked over for resolution by a special committee after a self-governing authority is established.

U.S. officials hope that these decisions will help pump new vigor into the negotiations, which have been stalled for 10 months. That apparently was what led Carter, at the swearing in ceremony for Alfred Moses, his new adviser on Jewish affairs, to say:

"We had a remarkably good meeting with Prime Minister Begin.The obstacles that now exist are much less formidable."

Later, at his news conference, Carter added: "We have faced much more formidable obstacles in the past" during his 1978 Camp David summit meeting with Begin and Sadat and in the negotiations leading to last year's Egyptian-Israeli peace treaty.

The president conceded that there are "differences of interpretation" between Israel and Egypt over specific aspects of the current talks, including the method for choosing a self-governing authority.

But he insisted that Begin and Sadat are committed to the success of the Camp David accords, and he stressed his belief that an autonomy agreement eventually will fall into place.