Despite deep scepticism among diplomats and many officials on both sides, the United States hopes the talks could result in a deal on creating a Palestinian state before Bush leaves office in January 2009.
"The parties have said that they are going to make efforts to conclude it in this president's term," Rice told reporters. "So ... that's what we'll try and do. Nobody can guarantee that. All you can do is make your best effort."
She also said it was possible that a peace deal struck by Abbas could eventually bring along Hamas supporters if they saw a "tangible" possibility of a Palestinian state.
"It isn't the first time in either international politics or human history that a legitimate government has not controlled all of its territory and had to find a way to re-establish authority," she said of the West Bank-Gaza split.
Hamas's militant Izz el-Deen al-Qassam Brigades issued a statement putting Abbas on notice that "ceding any inch of Palestine is a national and moral crime."
Mahmoud al-Zahar, a senior Hamas leader, said the group and allied factions would hold a "National Conference to Preserve Constant Rights" in the Gaza Strip to demonstrate their opposition to any concessions by Abbas.
With the conference less than a week away, Israeli and Palestinian teams were still trying to draft a joint document that would address in general terms issues such as borders and the future of Jerusalem and Palestinian refugees.
Looking ahead to post-conference negotiations, Olmert has said he would not put any future peace deals into motion until Palestinians fulfilled their commitments under a U.S.-backed road map, including reining in militants.
The 2003 peace plan also calls on Israel to freeze all settlement activity, an obligation it has not met.
A senior Israeli official said one sticking point was over how to oversee implementation of road map obligations.
Israeli negotiators have raised objections to setting up a trilateral monitoring committee with the Palestinians and the United States, citing fears Palestinians could learn the identity of Israeli security sources.
The official said while Israel did not object to sole U.S. oversight over implementation of road map commitments, it wanted Washington's assessment to be nonbinding.
