RAMALLAH, West Bank — Israel ruled out talks and the vanquished Fatah Party rejected a joint government with Hamas after the Islamic movement's sweeping victory in Palestinian elections, in what could be first steps to isolate the militant group and freeze Mideast peace initiatives.

The U.S. and European nations declared Thursday that Hamas could not form a legitimate government unless it drops its demand to destroy Israel and renounces violence.

"If your platform is the destruction of Israel, it means you're not a partner in peace, and we're interested in peace," President Bush said. Similar statements came from other parts of the world.

European parliament members spoke of the possibility that donors would cut off vital aid, putting Hamas under extreme pressure to moderate its hardline positions. The U.S. consul in Jerusalem, Jacob Walles, said today it was too early to discuss the possibility.

Israel was unprepared for the Hamas landslide. Foreign and defense ministry scenarios put such a stunning blow to the long-ruling Fatah as a low probability, officials said.

But after the rout, Israel's acting prime minister, Ehud Olmert, quickly ruled out talks: "The state of Israel will not negotiate with a Palestinian administration if even part of it is an armed terrorist organization calling for the destruction of the state of Israel," Olmert said in a statement.

Fatah, turned out of office by Palestinians angry over its corrupt and inefficient government, offered no help to Hamas, catapulted into leadership after its first foray into parliamentary politics.

Fatah leaders decided late Thursday not to enter a joint government with Hamas.

By the numbers, Hamas does not need Fatah — it won 76 of the 132 seats in parliament, a clear majority. Fatah, the undisputed ruler of Palestinian politics for four decades, got only 43. But Fatah could help Hamas by serving as a conduit for talks with Israel.

A Hamas leader, Ismail Haniyeh, said today that he had asked Palestinian leader Mahmoud Abbas, Fatah's chief, to meet Sunday to discuss forming a new government. Abbas' office said no appointment has been made yet.

Abbas said separately that he would tap Hamas to lead the next government.

Palestinian Prime Minister Ahmed Qureia of Fatah and his Cabinet resigned Thursday to make room for a Hamas government.