Bush's claims of security progress in Iraq were jarred by the assassination of a Sunni sheik who revolted against al-Qaida and fought alongside Americans.

Abdul-Sattar Abu Risha, the most prominent figure in a U.S.-backed revolt of Sunni sheiks against al-Qaida in Iraq, was killed Thursday by a bomb, dramatizing the danger faced by people who cooperate with coalition forces.

Bush had met with the sheik 10 days ago during a visit to Anbar province. Bush said that after the sheik's death, a fellow Sunni leader pledged to continue working with the United States.

Bush said Anbar, once considered lost to al-Qaida, shows what can happen across Iraq. "They show al-Qaida that it cannot count on popular support, even in a province its leaders once declared their home base."

Bush said he had directed Petraeus and Ryan Crocker, the U.S. ambassador to Iraq, to report to Congress in March with their next assessment of developments in Iraq and the level of U.S. troops needed to handle security.

"Americans want our country to be safe and our troops to begin coming home from Iraq," Bush said. He said his strategy would permit "people on opposite sides of this difficult debate to come together."

Polls show Americans overwhelmingly disapprove of Bush's handling of the war, which has claimed the lives of more than 3,700 U.S. troops and cost about a half-trillion dollars. His approval rating — both for his handling of Iraq and for his overall performance — stood at 33 percent in an Associated Press-Ipsos poll released Thursday.

In his speech, Bush directed specific messages to different audiences.

To Congress, he sought support for Petraeus' recommendations on troop levels.

To Iraqis, he said, "You must demand that your leaders make the tough choices needed to achieve reconciliation."

To Iraq's neighbors, he said efforts by Iran and Syria to undermine the government in Baghdad must end and that "the violent extremists who target Iraq are also targeting you."

To the international community, he appealed for help in revitalizing Iraq's economy and support for an expanded mission of the United Nations in Iraq.

To U.S. military personnel, intelligence officers, diplomats and civilians on the front lines, he said, "You have done everything America has asked of you."