The Bush administration announced Tuesday that it would hold a stripped-down international conference next week to begin negotiating the core issues that divide the Israelis and Palestinians, the first formal attempt to revive peace talks in seven years.

U.S. officials issued invitations to 49 nations and international organizations for the three-day gathering, to be attended by Israeli Prime Minister Ehud Olmert and Palestinian Authority President Mahmoud Abbas. The talks are aimed at building support for the wider peace negotiations and laying the groundwork for a Palestinian state in the next 14 months, before President Bush leaves office.

David Welch, the assistant U.S. secretary of State for the Middle East, said the agreement by the Israeli and Palestinian leaders to enter formal talks represented a "signal moment" that transforms the outlook for the long-stagnant peace process.

"There is a common understanding that this is the moment in which they can change the picture and get a serious negotiation started," Welch said at the State Department. "And that is hugely important to each of them."

But the two sides are preparing to begin the process without basic agreements on the subjects or ground rules of the talks, leaving prospects uncertain for such a high-stakes diplomatic maneuver. One report Tuesday by the International Crisis Group mirrored wide international concern by concluding that the talks were occurring in a "highly politicized" context, with both Israelis and Palestinians divided among themselves.

"Failure of the negotiations could discredit both leaderships, while further undermining faith in diplomacy and the two-state solution," the think tank's report said.

Casting the gathering in broad terms, Welch said no issue would be off-limits in meetings Monday and Wednesday at the White House and State Department or at the conference itself Tuesday at the U.S. Naval Academy in Annapolis, Md. Participants will decide how to continue talks after the Annapolis conference ends.

Bush, who first raised the possibility of a conference in July, helped clear the way for next week's gathering by telephoning two leaders who could play the roles of spoilers -- King Abdullah of Saudi Arabia and President Vladimir V. Putin of Russia. Administration officials did not describe the outcome of those calls.

Tuesday's U.S. announcement followed months of rancorous preparatory talks, and came a mere six days before the meetings. State Department officials scrambled Tuesday to finalize details and formally set the conference date, missing two scheduled announcement events in the process.

The invitees for the meeting include a long list of Arab countries, members of the United Nations Security Council, other world powers, and organizations such as the European Union, the World Bank, and the International Monetary Fund.

U.S. officials said they had not received responses from such key invitees as Saudi Arabia, but expressed confidence that the important players would attend.

"We're hopeful and expectant that Arab countries will participate because this is a serious effort," Welch said.

Despite the administration's optimism, the negotiations that begin next week face formidable obstacles and deep skepticism across the Mideast and elsewhere.

The prime sponsors -- Bush, Abbas and Olmert -- are seen as weak leaders with feeble domestic support. And despite consultations throughout the year, the Palestinians and Israelis have committed themselves to little more than continuing to talk about the issues.

Secretary of State Condoleezza Rice, the chief force behind the effort, began the year hoping that Palestinians and Israelis could inject new interest into a stalled process by opening discussions of how an eventual Palestinian state would look.

The conference is politically important to the main participants. Progress could provide a needed foreign policy boost for the beleaguered Bush administration, and could strengthen Abbas in his struggle against the more militant Palestinian faction Hamas. Positive steps also stand to bolster the Arab coalition aligned against Iran.

But the negotiating teams that began trying in early October to work out a crucial "joint statement" for the peace conference failed to agree on anything after 10 sessions -- neither the principles that would underpin the negotiations, a timetable or a mechanism for monitoring compliance with certain obligations.

After Olmert told Rice that concessions for such a document could bring down his government, she quietly reversed course.

"She was about to crash and hit a wall," said David Makovsky, director of the Mideast peace program at the Washington Institute for Near East Policy, adding that Rice "has learned the limits of power."

Now, the only agreement between the two sides is to simultaneously discuss two sets of issues: the short-term questions of Israeli security and settlements, which have preoccupied their talks in recent years; and the long-range core issues of Palestinian refugees, borders and the holy city of Jerusalem that underlie the dispute.

This agenda is a slightly more ambitious version of the moribund "road map" that the Bush administration issued in 2002.

As the administration has laid plans for the meeting, the two sides continue to disagree about the contentious issue of the timetable. The Palestinians are pressing for an eight-month deadline for finishing the negotiations, to ensure that a peace deal can be finished before Bush leaves office.

The Israelis have been unwilling to commit themselves to a deadline; Olmert said recently only that the talks might conclude within Bush's term.

Planning discussions were expected to continue up until the start of the conference. As of Tuesday, the two sides were still far apart, and officials on both sides said it was possible that they might issue no joint statement at all.

Another source of suspense is whether the Saudi government will show support by sending its foreign minister or another high-level official. Saudi support would signal that the Arab world was behind Abbas' efforts and would strengthen his hand in negotiations; by showing a greater Saudi acceptance of Israel, it could also boost Olmert at home.

Though the Saudis have let it be known that they are disappointed that the Israelis have not made more concessions, U.S. officials believe they will appear at the meeting, in part so they don't risk blame if the talks fall apart.

On Tuesday, Egyptian President Hosni Mubarak showed his support for the meeting as he received a visit from Olmert. But he recognized the prevailing pessimism over its prospects.

"Let's wait for the Annapolis conference and let's not say it is a failure until then," Mubarak said. "There are maybe obstacles, but we have to work towards overcoming them."

Another issue is whether the Syrian government will take part. U.S. officials, contradicting their policy of limiting contacts with Damascus, have invited the government of President Bashar Assad. Welch, in comments to reporters, promised that if Syrian officials came "we will not turn off the microphone for anyone."

Syrian officials have not made their intentions clear, but have canceled a "counter-conference" that was to be held at the same time -- a move U.S. officials interpreted as a good sign.

Another key question in the minds of Arab leaders and others involved with the issue is the commitment of Bush. The president has given Rice permission to try to restart talks. But many observers believe that he has been reluctant to have the United States play its traditional active role, offering proposals that can move the talks forward.

"That is the perception throughout the region," said Daniel C. Kurtzer, who was U.S. ambassador to Israel from 2001 to 2005 and is coauthor of a book on U.S. Mideast peace efforts.

Former U.S. negotiators, including those who tried to work out a peace deal for President Clinton in 2000, said they were surprised that the administration would try to rekindle the effort in the waning days of Bush's second term.

"After a determined effort by the Bush administration to avoid a peace process, now they're about to start one," said Martin Indyk, a former assistant secretary of State in the Clinton administration.

But he said that even though skepticism about the prospects for success was natural, after seven "miserable years" of violence in the region, the relaunch "is worthwhile in and of itself."