US military challenges Bush's troops plan

The paper, citing unnamed US officials familiar with the "intense" debate, said the Joint Chiefs of Staff unanimously disagree with the plan, in part because the force's mission has not been defined.

The Joint Chiefs believe the White House is pushing the plan for more troops partly because of limited alternatives, according to the Post.

Top Pentagon officials have told President George W. Bush that a short-term troop increase could give a boost to virtually all the armed factions in Iraq, without strengthening the position of the US military or Iraq's security forces in the long term, the Post reported.

An unnamed senior Bush administration official told the newspaper that it is "too simplistic" to say the White House and the Pentagon are fighting over whether to send more troops, but did say the military has questioned the option.

US troop levels in Iraq have dipped to 129,000 over the past week but have generally hovered around 140,000.

Plummeting public support for the Iraq war at home has spurred the president to conduct a major strategy review, set to be announced in early January.

Meanwhile, Robert Gates, sworn in as US defence secretary on Monday, said he understood the desire to bring troops home but that failure in Iraq would be a "calamity" that haunts and threatens America for decades.

"All of us want to find a way to bring America's sons and daughters home again. But, as the president has made clear, we simply cannot afford to fail in the Middle East," Gates said at the Pentagon.

"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," he said.

The 63-year-old former CIA director acknowledged during his Senate confirmation hearings in December that the United States was not winning in Iraq, but said it was not losing either.

Gates was officially sworn in at 7:03 am EST by White House Chief of Staff Joshua Bolten in the chief of staff's office. Later, he was ceremonially sworn in at the Pentagon by Vice President Dick Cheney, one of the Bush administration's strongest defenders of the Iraq war.