WASHINGTON, D.C. (AP) - President Bush, defending an unpopular war, ordered gradual reductions in U.S. forces in Iraq on Thursday night and said, "The more successful we are, the more American troops can return home."

Still, Bush firmly rejected calls to end the war, saying the insurgents who threaten Iraq's future are a danger to U.S. national security. American troops must stay in the battle, Bush said, and more than 130,000 will remain after the newly ordered withdrawals are completed in July.

"The principle guiding my decisions on troop levels in Iraq is: return on success," the president said.

Bush said 5,700 U.S. forces would be home by Christmas and that four brigades - at least 21,500 troops - would return by July, along with an undetermined number of support forces. Now at its highest level of the war, the U.S. troop strength stands at 168,000.

With no dramatic change in course, Bush's decision sets the stage for a fiery political debate in Congress and on the 2008 presidential campaign trail. Democrats said Bush's modest approach was unacceptable.

Click to watch President Bush's full speech - Sen. Jack Reed of Rhode Island, a former Army Ranger whodelivered the Democratic response, said that "once again, thepresident failed to provide either a plan to successfully end thewar or a convincing rationale to continue it." Reed said Democrats would work to "profoundly change ourmilitary involvement in Iraq." The reductions announced by Bush represented only a slighthastening of the originally scheduled end of the troop increasethat Bush announced in January. When the cutbacks are complete,about 132,000 U.S. forces will be in Iraq. Bush's speech was the latest turning point in a 4½-year-old warmarred by miscalculations, surprises and setbacks. Almost since the fall of Baghdad, in April 2003, U.S. commandersand administration officials in Washington mistakenly believed theywere on track to winding down U.S. involvement and handing off tothe Iraqis. Instead, the insurgency intervened and the reality of acountry in chaos conspired to deepen the U.S. commitment. Bush said the U.S. engagement in Iraq will stretch beyond hispresidency, requiring military, financial and political supportfrom Washington. He said Iraqi leaders "have asked for an enduringrelationship with America. "And we are ready to begin building that relationship in a waythat protects our interests in the region and requires many fewerAmerican troops." Bush described the withdrawals, and the U.S. forces stillfighting in Iraq, as a compromise on which war supporters andopponents could agree. "The way forward I have described tonight makes it possible,for the first time in years, for people who have been on oppositesides of this difficult debate to come together," Bush said. That appeared highly unlikely, however, based on the reaction ofDemocratic leaders who want deadlines for withdrawals. "The American people long ago lost faith in the president'sleadership of the war in Iraq because his rhetoric has nevermatched the reality on the ground," said House Speaker NancyPelosi, D-Calif. "The choice is between a Democratic plan forresponsible redeployment and the president's plan for an endlesswar in Iraq." Majority Democrats in Congress are unable to muster enough votesto force an end to the war. So they are hoping to win Republicansupport with legislation to limit the mission of U.S. forces totraining Iraq's military and police, protecting U.S. assets andfighting terrorists. Addressing America's frustration with the protracted war, thepresident said, "Some say the gains we are making in Iraq come toolate. They are mistaken. It is never too late to deal a blow toal-Qaida. It is never too late to advance freedom. And it is nevertoo late to support our troops in a fight they can win." "Whatever political party you belong to, whatever your positionon Iraq, we should be able to agree that America has a vitalinterest in preventing chaos and providing hope in the MiddleEast," the president said. He added, "Let us come together on a policy of strength in theMiddle East." In his speech, Bush acknowledged that Iraq's government hasfailed to meet goals for political reconciliation and security."In my meetings with Iraqi leaders," he said, "I have made itclear that they must." A White House report, to be released Friday, will document thefailures of the Iraqi government. The latest conclusions largely track a comparable assessment inJuly, the White House said. The earlier report said the Iraqigovernment had made satisfactory gains toward eight benchmarks,unsatisfactory marks on eight and mixed results on the rest. Asenior administration official said Thursday that only one of thebenchmarks - enacting and implementing legislation to allow formerlower ranking members of Saddam Hussein's Baath Party to holdgovernment positions - has moved from unsatisfactory tosatisfactory. The official, who spoke on condition of anonymity because thereport had not been made public, pointed to the tentative Aug. 26power-sharing agreement among leading Iraqi politicians thatoutlined major terms on several issues, including changing the lawpreventing many former Baath Party members from holding governmentjobs and elected office. "Iraq's national leaders are getting some things done," Bushcontended. He said the Baghdad government has passed a budget andis sharing oil revenues among the provinces even though legislationhas not been approved. Changes that have begun to take hold in theprovinces must be followed in Baghdad, he said. Bush's claims of security progress in Iraq were jarred by theassassination of a Sunni sheik who revolted against al-Qaida andfought alongside Americans. Abdul-Sattar Abu Risha, the most prominent figure in aU.S.-backed revolt of Sunni sheiks against al-Qaida in Iraq, waskilled Thursday by a bomb, dramatizing the danger faced by peoplewho cooperate with coalition forces. Bush had met with the sheik 10 days ago during a visit to Anbarprovince. Bush said that after the sheik's death, a fellow Sunnileader pledged to continue working with the United States. "And as they do," the president said, "they can count on thecontinued support of the United States." He said Anbar, once considered lost to al-Qaida, shows what canhappen across Iraq. "They show al-Qaida that it cannot count onpopular support, even in a province its leaders once declared theirhome base." Bush said he had directed Petraeus and Ryan Crocker, the U.S.ambassador to Iraq, to report to Congress in March with their nextassessment of developments in Iraq and the level of U.S. troopsneeded to handle security. "Americans want our country to be safe and our troops to begincoming home from Iraq," Bush said. He said his strategy wouldpermit "people on opposite sides of this difficult debate to cometogether." Polls show that Americans overwhelmingly disapprove of Bush'shandling of the war, which has claimed the lives of more than 3,700U.S. troops and cost about a half trillion dollars. His approvalrating - both for his handling of Iraq and for his overallperformance - stood at 33 percent in an Associated Press-Ipsos pollreleased Thursday. In his speech, Bush directed specific messages to differentaudiences. To Congress, he sought support for Petraeus' recommendations ontroop levels. To Iraqis, he said, "You must demand that your leaders make thetough choices needed to achieve reconciliation." To Iraq's neighbors, he said efforts by Iran and Syria toundermine the government in Baghdad must end and that "the violentextremists who target Iraq are also targeting you." To the international community, he appealed for help inrevitalizing Iraq's economy and support for an expanded mission ofthe United Nations in Iraq. To U.S. military personnel, intelligence officers, diplomats andcivilians on the front line, he said, "You have done everythingAmerica has asked of you."