Israeli Prime Minister Menachem Begin summoned American Jewish leaders to his side here tonight in an effort to solidify support for what he termed new compromises by Israel in the latest draft of an Egyptian-Israeli peace treaty.

Begin met for almost two hours tonight with members of the Conference of Presikdents of Major American Jewish Organizations, an important coalition of the leaders of the principal Jewish groups in the country.

Participants in the meeting described him as "satisfied" and "optimistic" and quoted him as saying that Israel and the United States are now in "complete agreement" about the terms of a peace treaty.

But Begin, asked if the peace negotiaions could still fall apart, was cautious as he placed the burden of the next step in the process on Egyptian President Anwar Sadat.

"It all depends on the reply to be given by President Sadat," Begin told reporters after the meeting. "I do hope he will give a positive reply" to the latest peace proposals.

Begin's whole day amounted to a low-keyed soft sell in which Israel was depicted as the compromiser, and the next and probably critical step in the negotiations was laid at the doorstep of Egypt.

Earlier, the prime minister had breakfast with more than 20 American journalists at which, according to an Israeli official, he charchterized those proposals as requiring important compromises by Israel.

But Begin declined to desvribe the proposals, suggested by Carter Sunday afternoon and approved Monday by the Israeli cabinet, or to offer other descriptions or characterizations of them. His unusual reticense reflected the rapid pace of developments in the peace process which, among other things, shortened and changed the complexion of his visit to New York.

Begin arrived in the United States last Thursday describing the peace negotiations the draft treaty as "a sham document" that Israel would never sign. As his intial talks with Carter at the White House seemed to be getting nowhere, Israeli officials prepared for a public relations blitz of New York to offset what many feared would mark the collapse of the peace process begun last September at Camp David.

But that strategy suddenly changed on Sunday when Carter offered new U.S. proposals for changes in the draft treaty's language, and on Monday, when the White House announced that the president will fly to Cairo on Wednesday to present the American suggestions to Sadat, and go on from there to Jersalem on Saturday.

Begin had planned to remain in New York at least until Thursday, and possibly longer, depending on developments. Now, Begin is scheduled to depart here Wednesday noght. More importantly, he canceled a number of scheduled interviews for fear that public comments on the eve of Carter's trip to the Middle East cold upset the delicate negotiating process.

Instead, the prime minister spent most of today secluded in his room at the Regency Hotel on Park Avenue, conferring privately with what his press secretary, Dan Pattir, described as "old friends."

Among those Gegin conferred with today by telephone today was former secretary of state Henry A. Kissinger, who was vacationing in Acapulco. Begin also spoke with former Israeli prime minister Yitzhak Rabin.

Begin is still scheduled to speak here Wednesday to about 2,000 Jewish leaders despite the misgivings of some leaders of Jewish groups that extemporaneous remarks by the prime minister in what is bound to be an emotional atmosphere could dndanger Carter's mission.

The normally outspokken Begin thus took pains not to appear to be putting pressure on Sadat to accept the Israeli-approved proposals before the Egyptian president even sees them.

However, there was no question here today that the Israeli delegation considers the next move up to Sadat, as suggested by Begin's assertion that Israel has already made new compromises in accepting Carter's latest suggestions.

Nor did it seem likely that Begin would have trouble lining up the support he seeks from the American Jewish community.In a statement before the meeting issued from Jerusalem where he is visiting, Maxwell E. Greenberg, national chairman of the Anti-Defamation League of B'nai B'rith who would normally have been among those conferring with Begin, said:

"Israel has again demonstrated its willingness to take serious risks to achieve friendly relations with its neighbors. We hope that Egupt will avoid injecting -- again -- new demands whihc are obstacles to agreement, and that the United States will use its strength to prevent further Egyptian dilution of its minimal concession."

Emerging from his breakfast with the journalists, Begin seemed optimistic. "I'm always optimistic about these things," he said about the prospect of a peace treaty signing soon. "I can't give days, who can?"