JERUSALEM -- Prime Minister Yitzhak Shamir, yielding to mounting pressure yesterday, gave a conditional "yes" to a U.S.-Soviet-sponsored Middle East peace conference, leaving Palestinians as the only group yet to agree to participate.
Mr. Shamir's acceptance hinges on Israel's being satisfied with the membership of a joint Palestinian-Jordanian delegation, the matter that has blocked previous peace efforts and that Secretary of State James A. Baker III has so far failed to resolve.
Interviewed on Israeli television last night, Mr. Shamir claimed that the United States had agreed to Israeli conditions for the makeup of the Palestinian delegation -- exclusion of Palestine Liberation Organization members, residents of East Jerusalem and Palestinians living outside the Israeli-occupied territories. U.S. officials refused to describe any assurances given to Israel.
The prime minister agreed in principle to terms he rejected seven weeks ago and is to seek backing from his Cabinet on Sunday, when he risks an acrimonious debate and a walkout by extreme right-wing parties.
But Mr. Shamir's political position appears impregnable. Even if all the extreme right parties left the government, he could continue to control a narrow majority in Parliament. In addition, the left-of-center Labor Party promises to support Mr. Shamir as long as he continues with the peace process.
Emerging from a meeting with Mr. Baker, Mr. Shamir said: "We have . . . expressed our readiness to enter peace negotiations in accordance with the U.S. proposal, subject to a satisfactory solution of the issue of Palestinian Arab representation" in a joint delegation with Jordan.
Mr. Baker, buoyant that months of shuttle diplomacy were finally bearing fruit, said, "I think that the prospect of Arab-Israeli peace discussions [is] no longer simply a dream." He called Mr. Shamir's announcement "extraordinarily positive."
Mr. Shamir's answer came a day after President Bush and Soviet President Mikhail S. Gorbachev, at their Moscow summit, announced plans to convene a Mideast peace conference in October, to be followed by direct talks by Israel, Arab states and Palestinians.
The conference and subsequent face-to-face talks are intended to produce a comprehensive settlement of the Arab-Israeli conflict based on United Nations resolutions calling for an exchange of territory for peace.
In recent telephone conversations between Mr. Baker and Mr. Shamir, the secretary "made clear to him . . . it was very important for us to be able to go out and say, 'Israel says yes to peace under the circumstances,' " a senior Bush administration official said.
Syria, Jordan and Lebanon -- all neighbors of Israel -- have accepted the U.S. terms for the peace talks.
Mr. Baker is due to meet with a three-member Palestinian delegation today, but a senior U.S. official said last night he was unsure whether the meeting would take place.
The Israeli acceptance has increased pressure on Palestinians to do the same. But U.S. officials say they do not know if the Palestinian delegation will give a formal response today.
Palestinians oppose Israel's having a say in the makeup of the Palestinian delegation. They want to use the peace conference as a platform to demand statehood in the West Bank, with Jerusalem as the capital.
Mr. Shamir underscored the importance of the Palestinian issue. "I said that Israel will be prepared and willing to participate in the process on condition that this problem -- the Palestinian problem -- will be resolved to our liking," he said on state television.
"If we're offered a solution that we cannot accept, then the whole situation will be altered," he said.
Palestinian leaders gave no hint of willingness to compromise. "A yes with conditions is a no in fact," Hanan Ashrawi, a Palestinian representative who has met with Mr. Baker, told wire services. "The Palestinians insist on choosing their own delegates to talks."
A favorable Cabinet vote Sunday and a favorable response from Palestinians do not guarantee a conference. In addition to setting conditions for a Palestinian delegation, Israel is asking for other, procedural guarantees from the United States.
Mr. Shamir said U.S. and Israeli officials are to draw up a memorandum listing assurances to Israel. Israeli officials are demanding that it include guarantees on procedures in order to safeguard Israel's interests on substantive issues. U.S. officials say the assurances will be shared with other parties.
After meeting the Palestinians, Mr. Baker is to fly to Jordan, where he is to discuss the makeup of the Palestinian-Jordanian delegation with King Hussein. He also is to fly to Algeria, Morocco and Tunisia -- headquarters for the PLO. State Department officials said there will be no talks with PLO officials.
A senior U.S. official said he hoped the three North African countries also could be persuaded to join multilateral talks on regional problems such as arms control that would follow the peace conference.
"We would like to see any parties who have influence . . . [get an] opportunity here to prove [former Israeli Foreign Minister] Abba Eban wrong when he said, 'The Palestinians never pass up an opportunity to pass up an opportunity.' "