Reacting to Hamas's suprise win in Wednesday's Palestinian parliamentary election, Bush said he would not talk to a party that advocates the destruction of a US ally.
"I have made it very clear, however, that a political party that articulates the destruction of Israel as part of a platform is a party with which we will not deal," he told a White House news conference.
Acting Israeli Prime Minister Ehud Olmert has also said he will refuse to negotiate with a Palestinian government that includes Hamas.
"If a government is led by or includes Hamas, the Palestinian Authority will turn into a terror organisation," he said.
Acting Foreign Minister Tzipi Livni called on the European Union and other states not to deal with what she called a "terror government."
The suprise outcome of the Palestinian vote is now certain to be a key issue in Israel's own election scheduled for 28 March.
Commenting on the outcome of the vote, Bush urged Palestinian President Mahmoud Abbas to stay in office so the US could keep open a diplomatic channel with the Palestinian government.
"Peace is never dead, because people want peace"
The Bush administration, which has made promoting democracy in the Middle East a priority for its second term, had pressed Abbas to hold Wednesday's parliamentary election despite polls showing Hamas would do well.
Analysts have said Hamas's shock victory, giving it 76 seats in the 132-seat parliament, could bury any hope of reviving peace talks with Israel and stop Bush from achieving his goal of a settlement creating two states within the next few years.
However, Bush rejected susggestions that the Hamas win had finally killed off the stalled peace process.
Abbas says he will continue to
pursue negotiations with Israel
"Peace is never dead, because people want peace," he said.
Hamas's win brought an end to four decades of rule by the Fatah Party founded by the late Yasser Arafat.
Their victory stunned even Hamas leaders, who mounted a well-organized campaign but have no experience in government.
They have offered to share power with President Mahmoud Abbas, the Fatah chief, who has said he may go around the new government to talk peace with Israel.
"I am committed to implementing the programme on which you elected me a year ago," he said in a televised speech. "It is a programme based on negotiations and peaceful settlement with Israel."
Final results results are to be certified within two weeks. During that time, participants may challenge results.
After final results are in, Mahmoud Abbas, the president
of the Palestinian Authority, begins consultations with
factions that are to enter the next parliament, then will tap a party to put together a government. That party will
have three weeks to put together a government, and can ask for a two-week extension.
The new Palestinian parliament is to be sworn in for a four-year term in March.
Abbas, elected last year to a four-year term, can remain in office. He has said he would step down if he cannot push
forward efforts to seek a peace deal with Israel.
Nonetheless the cabinet and legislature must approve any major initiative by the Palestinian president, giving Hamas tremendous influence over peace moves.
Abbas, who was elected last year to a four-year term as president of the Palestinian Authority, has yet to decide how closely to work with the group.
Fatah legislator Saab Erekat said his party had decided not to join a Hamas government.
"We will be a loyal opposition and rebuild the party," Erekat said after meeting with Abbas.
In the aftermath of Hamas's victory, the US, which along with the European Union lists Hamas as a terrorist organisation, held emergency telephone talks with the rest of the so-called Quartet of major powers trying to mediate an end to conflict between Israel and the Palestinians.
"We reaffirmed the view that ... you can't have one foot in terror and the other in politics," US Secretary of State Condoleezza Rice told Reuters in an interview after the talks.
The Quartet brings together the US, EU, Russia and the United Nations.
Hamas wooed voters with an
In a statement, the Quartet demanded Hamas renounce violence, accept Israel's right to exist, and disarm.
Leaders of the EU, the biggest donor to the aid-dependent Palestinian Authority, said Hamas risked international isolation if it did not comply.
Hamas, which wooed voters with anti-corruption credentials and charity work as well as its attacks on Israel, has rejected any suggestion it would disarm, though it has largely followed a ceasefire for nearly a year.
"The US administration and European countries should put pressure ... on the occupier and not the occupied and displaced Palestinian people," said senior Hamas official Ismael Haniya.
However another leading Hamas official Mahmoud Zahar said the group would extend its year-old truce if Israel reciprocates.
"If not, then I think we will have no option but to protect our people and our land," he said.
Commentators in the Arab world have predicted pragmatism would eventually oblige Hamas to soften its position and Israel to talk to the new Palestinian leaders.
With peace talks stalled since 2000, Israel has hinted that it might make unilateral moves to set a border with the Palestinians if there are no more negotiations.
Israel has already pulled its settlers out of the Gaza Strip without negotiations.