By Matt Spetalnick WASHINGTON, Jan 11 (Reuters) - U.S. President George W. Bush faced a brewing showdown against a hostile Democratic-controlled Congress on Thursday over his plan to send more forces to Iraq in defiance of U.S. public opinion. In a bid to rally support for the unpopular war, Bush told Americans on Wednesday night that 21,500 extra troops were needed to help "break the cycle of violence" in Iraq and hasten an eventual withdrawal. The buildup plan put the president on a collision course with the new Democratic congressional leadership, which called it an escalation of U.S. involvement in a war that has killed more than 3,000 Americans and tens of thousands of Iraqis. Delivering a long-awaited address on his Iraq strategy, Bush offered a sober assessment of the nearly 4-year-old war that included the president's first admission that he had erred by not sending more troops sooner. "Where mistakes have been made, the responsibility rests with me," he said in a televised speech from the White House. A boost in troop levels, mostly aimed at quelling sectarian strife in Baghdad, goes counter not only to Democratic demands but to the recommendations of an elite panel on Iraq, which had urged a U.S. pullback from combat by early 2008. "We concluded that to step back now would force a collapse of the Iraqi government, tear that country apart and result in mass killings on an unimaginable scale," Bush said. Congressional Democrats, who swept to power in November elections in what was widely seen as an anti-war referendum, vowed to challenge Bush as he enters his final two years in office. "The president is accelerating the same failed course he has pursued for nearly four years. He must understand that Congress will not endorse this course," said U.S. Sen. Edward Kennedy, a Massachusetts Democrat. DEMOCRATIC SCRUTINY Democrats pledged close scrutiny of Bush's plan plus non-binding votes in Congress, forcing his fellow Republicans to choose between breaking with him or embracing an unpopular policy just as the 2008 U.S. presidential race gears up. But Democrats themselves appeared reluctant to cut off funding for the increased forces, which would allow Bush and his allies to accuse them of abandoning American troops. He will ask Congress for $5.6 billion for the extra deployment and another $1.2 billion for a rebuilding and jobs in Iraq. Secretary of State Condoleezza Rice and Defense Secretary Robert Gates were expected to face heavy grilling on Iraq in appearances before congressional committees on Thursday. Signaling growing impatience, Bush used blunt language to warn Iraqi Prime Minister Nuri al-Maliki that "America's commitment is not open-ended." But Bush still faced a tough sell with the American public, which polls have shown strongly opposed to a troop increase. Military analysts said Bush's plan, which calls for 17,500 more troops for Baghdad and 4,000 more for restive Anbar province, had no guarantee of success after the failure of several similar offensives. While the increase will take the number of U.S. troops in Iraq to more than 153,000, the United States has had more boots on the ground in the past and still failed to stop the spiral of deadly violence. Bush set no time limit for the new deployment and offered no hint of a timetable for when troops might begin to withdraw. (Additional reporting by Steve Holland, Susan Cornwell and Rick Cowan)
