Cairo, Egypt ? Hamas rejected President Bush’s proposal for a Mideast peace conference, denouncing it Tuesday as nothing but lies, while Syria said it fears the offer is “just words.”

Without cooperation from key Arab players, Bush’s last major push for a Mideast breakthrough could falter.

Washington’s close Arab allies, including Egypt, Saudi Arabia and Jordan, welcomed Bush’s proposal, but stressed the importance of making an Arab land-for-peace proposal first adopted in 2002 key to any talks. Israel’s support was also qualified, with Prime Minister Ehud Olmert’s spokeswoman saying it was too early to talk about full-fledged peace talks as long as Palestinian violence against Israel continues.

Bush called Monday for an international conference in the fall aimed at restarting peace talks between Israel and the Palestinians, saying it was a “moment of choice” in the Middle East. U.S. officials expressed hope that Arab countries, including moderate nations that do not have diplomatic relations with Israel, would attend.

The gathering is aimed at giving international support to U.S.-backed Palestinian President Mahmoud Abbas, whose forces were recently routed by the Hamas militant group in the Gaza Strip. With international backing, the moderate Abbas now heads an emergency government based in the West Bank.

Though the fall conference’s exact date, location, agenda and participants remain unknown, without support from Hamas and its main backer, Syria, there were doubts that the gathering would have much impact.

The White House played down the meeting’s importance Tuesday and said it was too early to say where or when it would take place. “I think a lot of people are inclined to try to treat this as a big peace conference,” said White House spokesman Tony Snow. “It’s not.”

A 1991 Mideast peace conference in Madrid paved the way for the Oslo peace accords and establishment of the Palestinian Authority. But repeated stalemates have since left many skeptical that a repeat of that gathering would lead to a major and enduring breakthrough.

Syria’s U.N. ambassador, Bashar Ja’afari, said the conference’s legitimacy hinged on the involvement of Syria and Iran.

Bush “did not elaborate on who would be invited. One minute before he declared this initiative, he attacked Syria and Iran,” Ja’afari said in New York. “That means he is excluding, somehow, Syria and Iran from this so-called international conference.”

Some also were skeptical of Bush’s motives.

“The Bush administration is driven by its failure in Iraq and its failure to secure support from U.S.-friendly Arab regimes for its regional policies,” said Amr Hamzawy, a Middle East expert at Carnegie Endowments, a Washington-based think tank.

“I read this morning that the American president spoke of his wish to work for a peace conference. I hope … this is true, but to this moment these are just words as far as we are concerned,” Syria’s President Bashar Assad said in an address to parliament after being sworn in for a second seven-year term in office.