A top Hamas (search) leader urged Arabs and Muslims late Monday to join forces to defend themselves against the United States and Israel and support the Palestinians in their worsening conflict with the Jewish state.

Khaled Mashaal (search), the political chief of the Palestinian militant group, described America and Israel as "the leading dangers" confronting Arabs and Muslims around the world.

The Syrian-based Hamas leader made his comments to about 500 people at a rally after a condolence ceremony at the Palestinian refugee camp of Yarmouk, outside Damascus, held for Abdel Aziz Rantisi (search), the Hamas leader in Gaza assassinated by Israel on Saturday.

"Arabs and Muslims have to join together in order to stand against the arrogance of the Zionists and the Americans," Mashaal said, adding that "Hamas will reply to the killing of Dr. Rantisi." He did not say how.

Mashaal's comments come amid Arab anger at Rantisi's killing and the Bush administration's endorsement last week of a proposal by Israeli Prime Minister Ariel Sharon (search) to withdraw from Gaza and parts of the West Bank in exchange for U.S. concessions on keeping Israeli settlements on other Palestinian-claimed land.

President Bush also embraced Israeli rejection of any "right of return" for Palestinian refugees after a White House meeting with Sharon.

"The Arab governments have to stop the Zionist-American plan to control the Arab world," Mashaal said. "The Palestinians have done their duties and offered martyrs in Palestine, and now the Arabs have to unite with the Palestinians."

In an interview with The Associated Press on Sunday, Mashaal blamed Washington for Rantisi's death, saying the Bush administration's endorsement of Israel's proposal to hold onto West Bank Jewish settlements encouraged Sharon to give the go-ahead for the Hamas leader's killing.

Rantisi was killed less than a month after becoming Hamas' chief in Gaza following Israel's assassination of the militant group's previous leader, Sheik Ahmed Yassin.

Mashaal, whom Israeli officials have also targeted for assassination, said Hamas has appointed a replacement for Rantisi in Gaza but has not released his identity.

Mashaal's outspoken speeches have become more regular since Yassin's and Rantisi's deaths, marking a shift in the apparent Syrian crackdown on Damascus-based Palestinian groups after the United States last year began urging Syria to curb the influence of anti-Israeli groups operating on its soil.

In December, Bush signed legislation calling for sanctions against Syria if it maintains its purported support of militant groups and terrorists involved in the insurgency in Iraq.

The Bush administration is still assessing how to administer the legislation.

Syria has said it has closed Palestinian militants' offices in Damascus and insists the militant groups are not terrorists but fighters resisting Israeli occupation of their homeland. It also says it is trying to prevent fighters from crossing its border into Iraq and denies it is pursuing weapons of mass destruction.