Secretary of State Condoleezza Rice said Thursday she was encouraged by a round of furious Mideast diplomacy to prepare a U.S.-hosted peace conference in the fall despite divisions between Israel and the Palestinians that could derail it.

With tensions running high and time running out to plan the meeting, a senior U.S. official said Rice would return to the region at the end of October or early November after National Security Adviser Stephen Hadley goes there next week to press the two sides to launch formal peace talks.

Hadley's trip, so close on the heels of Rice's visit this week, is intended to move the two sides closer and underscore U.S. commitment to the creation of a Palestinian state, the official said.

Rice said four days of intense discussions with Israeli and Palestinian officials had convinced her they are serious about forging a document that, when endorsed at the conference in late November or December, would start the negotiations.

At the same time, she acknowledged that planning for the meeting in Annapolis, Md. was entering its most difficult phase with the parties at deep odds over the substance of the joint declaration — differences that could force a delay or cancellation of the session.

"I think they are very serious," she said. "The teams are serious, the people are serious, the issues are serious, so I am not surprised that there are tensions, I am not surprised there are some ups and downs.

"That is the character of this kind of endeavor, but I was encouraged by what I heard," she told reporters as she flew to London after her seventh Mideast trip this year during which she shuttled between Israeli Prime Minister Ehud Olmert and Palestinian president Mahmoud Abbas.

Rice's return trip also will take her to an Iraq neighbors' meeting in Istanbul, Turkey, said the official, who spoke on condition of anonymity because the trip plans had not been formally announced.

The flurry of diplomatic activity aims to push Israel and the Palestinians into consensus on the substance of the conference's joint declaration, which would outline a way for the two sides to return to the negotiating table after seven years of bloodshed and diplomatic paralysis.

The Palestinians and their Arab allies such as Egypt and Jordan are insisting the document be detailed and specific with a timetable for formal peace talks. The Israelis want language that is more vague.

Rice won public backing for the conference from a skeptical Egypt during a Tuesday stop in Cairo, and appeared to soothe Jordanian concerns at a private lunch in London with King Abdullah II on Thursday.

Abdullah voiced strong support for the conference after his talks with Rice and said he was encouraged to hear about progress she made, according to a royal palace statement released in Amman, Jordan.

"King Abdullah expressed hope that the meeting would mark a major milestone towards the establishment of an independent Palestinian state in the near future," according to the statement.

Addressing Israel, Abdullah said his peace partner — with whom Jordan signed a peace treaty in 1994 — must "show more political flexibility and to cease any activity that could raise tensions."

President Bush has promised that the conference and the declaration it is to produce will be "serious and substantive," pledges that Rice repeated at nearly all her public events this week.

Rice said the document should address core issues as the Palestinians want but stressed it need not be "detailed," saying it will be a starting point for formal talks and not a resolution of the conflict.

"All this document is trying to do is to demonstrate that they now believe they have a basis for pushing forward on the resolution of those outstanding issues," she said.

The Palestinians want the document to include at least a sentence or two on how to solve each of the major issues of dispute, such as borders and Jerusalem, which both sides want to claim as their capital.

The Palestinians' core demand is that the future border between Israel and Palestine be based on the pre-1967 Mideast War lines, with modifications through land swaps. Israel captured the West Bank and other areas in the 1967 war. But Israel has balked at such specificity.

During her trip, Rice scheduled numerous round-table meetings with civic, business and religious leaders from all sides in an effort to distinguish her work from previous failed U.S. Mideast peace efforts, notably the Clinton administration's abortive 2000 Camp David sessions.

Many of those discussions focused on the security and economic issues that will present themselves once a Palestinian state is created side-by-side with Israel.

"I am quite convinced that one of the really crucial pieces that has to be filled in are these concepts of how the states will relate to each other in practical terms concerning security and in practical terms concerning economic issues," she said.