New US Defence Secretary Robert Gates has said that resolving the conflict in Iraq will be "at the top of the list" as he was sworn in to replace the embattled Donald Rumsfeld.
"Failure in Iraq at this juncture would be a calamity that would haunt our nation, impair our credibility and endanger Americans for decades to come," Gates, 63, said in a ceremony at the Pentagon on Monday.
US President George W Bush dismissed Rumsfeld, 74, a day after his Republican Party was soundly defeated in the Nov 7 Congressional elections.
Bush has said he is seeking a "new way forward" for his policy in Iraq, which has been unable to defeat the insurgency or halt sectarian violence that has brought the country to the brink of full-blown civil war.
Gates said he would soon travel to Iraq to receive briefings from American military commanders, saying he expected their advice to be "unvarnished and straight from the shoulder".
Bush intends to outline his new strategy in early January, when his administration completes its review of the current policy and plots a fresh approach. Gates served on a congressionally appointed bipartisan commission assessing the situation in Iraq until Bush tapped him to replace Rumsfeld.
Gates, the director of the CIA from 1991 to 1993, was first sworn in at the White House in a private event before the public ceremony.
Gates spoke bluntly about the war in Iraq during his senate confirmation hearing on Dec 5, warning that sectarian conflict between Shias and Sunnis could spill into the rest of the Middle East. He also said he does not believe the US was winning in Iraq.
The senate went on to confirm him by a 95-to-two vote.