Facing mounting skepticism over the upcoming U.S.-led, Israeli-Palestinian peace summit, U.S. Secretary of State Condoleezza Rice told a massive gathering of Jews here that progress toward a two-state solution is vital to confronting Iran.

"What is at stake is nothing less than the future of the Middle East," Rice said Tuesday during an address to delegates at this week’s General Assembly of the United Jewish Communities.

"Violent extremists, with the government of Iran increasingly in the lead, are doing everything in their power to impose their fear, their resentments and their hate-filled ideologies on the people of the Middle East," she said. “This makes the two-state solution even more urgent than ever."

Asserting that Palestinian Authority President Mahmoud Abbas is a true peace partner, Rice said she fears that if "Palestinians reformers" fail to deliver on the Palestinian people’s hope for a state, then "the moderate center could collapse and the next generation of Palestinians will become lost souls of unbridled extremism."

"It is not a time for half measures," she said.

Rice's speech at the G.A. comes amid growing Jewish opposition to various proposals aimed at jump-starting Israeli-Palestinian talks and a mushrooming campaign to raise questions about whether the Palestinian leadership is committed to peace.

While the Bush administration praises Abbas, members of the Conference of Presidents of Major American Jewish Organizations are raising new questions about the Palestinian leader.

The Presidents Conference -- the Jewish community's main pro-Israel umbrella group -- is considering a resolution calling on Abbas to rescind any clauses in his Fatah party's constitution that challenge Israel's right to exist.

In addition, a growing coalition of Orthodox and right-wing organizations are mobilizing to head off any proposal on dividing or sharing Jerusalem with the Palestinians.

Last week, the New York Jewish Week, one of the most widely read Jewish newspapers in the country, published a column at the top of its front page slamming Rice's currents efforts.

In the column, titled "Rice's Folly," editor and publisher Gary Rosenblatt wrote that "diplomatic amnesia has descended on Washington once again."

A supporter of a two-state solution, Rosenblatt nonetheless echoed growing concerns among some influential Jewish organizations that a failed summit could end up triggering a fresh round of violence.

In an exclusive interview with JTA prior to her speech at the G.A., Rice rejected such concerns.

"No one can afford to fail here," the secretary of state said. "Not acting is failure in these circumstances."

"When you have a Palestinian partner who is dedicated against violence and against terrorism, and who’s struggling against an alternative view for the Palestinians," Rice told JTA, "not acting, I think, has much, much more significant risk than acting."

Citing a recent speech by Israeli Prime Minister Ehud Olmert, Rice said the goal is for the Annapolis summit to serve as a springboard for launching continuous negotiations on a two-state solution.

Rice praised several steps taken by Abbas and his loyalists in the West Bank to fight terrorism.

“Frankly, some of the things that they’ve done recently in terms of the closing down of charities, the freezing of bank accounts -- this is a very good start,” Rice told JTA. “The security operations that are going on in Nablus are a good start.”

During her speech, Rice was cheered multiple times when discussing the need to defend Israel, fight anti-Semitism and confront Hamas and Iran.

But the crowd was silent as she described Abbas as a true partner for peace and said the Palestinians now had “responsible leadership” with which Israel can deal.

“The question is not just whether we have the leadership, but what it can deliver,” Malcolm Hoenlein, executive vice chairman of the Presidents Conference, said after hearing Rice’s comments.

He noted that Israeli officials are skeptical of the Palestinian leadership’s ability to deliver on its promises, particularly when it comes to the security measures outlined in the early phases of the “road map” peace plan.

"The real danger is not to raise expectations that will lead to frustrations, rather than realistic, incremental goals that will show people where we are going," Hoenlein said. "People are looking to Annapolis to see whether they can come to an understanding on principles."

Aside from substance, there has been some confusion about the exact date and duration of the upcoming conference.

U.S. sources have said the gathering will take place the week of Nov. 26 but have not been more specific. Jerusalem sources said Monday the U.S.-hosted parley will take place Nov. 27 and be held over one day.

Expectations had been that the conference would last two or three days. If true, the shorter length suggests there will not be extensive talks on the prospects for Palestinian statehood.

Rice appeared to confirm that in her interview with JTA.

"They're not going to create the Palestinian state at Annapolis," she said. When asked if Saudi participation has been secured, she said no invitations had been sent out yet. “I don’t want to speculate about the participants,” Rice said.

She said the Israeli-Palestinian conference "is going to happen,” but that she did not expect the conference to last for "several days."

Further lowering expectations, Olmert said this week in Israel that at Annapolis he simply would seek to lay the groundwork for future peace negotiations with Abbas.

"It is a meeting; it is not a negotiating session," Olmert told his parliamentary faction. "But it is certainly a meeting intended to provide an opportunity for generating a diplomatic process between us and the Palestinians."

Rice told the G.A. audience that the Annapolis meeting would not replace the road map peace plan, nor would it supplant direct negotiations between the two sides. In addition to stressing the need for the Israelis and Palestinians to make tough decisions, Rice said America’s Arab allies need to do more to support the peace process.

“If our Arab friends of long standing truly desire peace,” Rice said, “then they need to demonstrate to their people and to the world that they believe Israel has a permanent home in the Middle East.”

JTA Washington bureau chief Ron Kampeas contributed to this report.