Baghdad bombs kill 105

Comparable figures for previous years were not available but officials agree sectarian bloodshed has surged in the past year.

"Without significant progress on the rule of law, sectarian violence will continue indefinitely and eventually spiral out of control," the U.N. human rights chief in Iraq, Gianni Magazzeni, told a news conference.

Of the 6,376 civilians killed in the last two months of 2006 -- 3,462 in November and 2,914 in December compared with a high of 3,702 in October -- three out of four were killed in Baghdad.

Maliki's government, which branded the last U.N. report as grossly exaggerated, has since banned its officials from giving casualty figures and the United States, which has run Iraq for four years, declined to vouch for the U.N. data.

Maliki and Bush are preparing a security crackdown in Baghdad, involving Iraqi and about 20,000 American reinforcements, which is widely portrayed as a last chance to avert a civil war between Sunnis and Shi'ites that could draw in Shi'ite Iran and Arab states on opposing sides.

Leaders of the Shi'ite majority say the plan to stifle militants with extra force, lasting six months or more, must break Shi'ite militias as well as Sunni rebels. Maliki has made that pledge before but Americans critical of Bush's new troop increase say they are skeptical he can deliver this time.

The White House said on Tuesday a planned non-binding congressional resolution against Bush's U.S. troop increase in Iraq could send a signal that America is divided on the war.

Some Bush critics on Capitol Hill think a non-binding vote is not enough. One Democrat with presidential ambitions, Sen. Chris Dodd of Connecticut, will unveil legislation on Wednesday demanding congressional approval for Bush's troop increase, Dodd's office said.

The Shi'ite deputy speaker of parliament said the new Iraq plan's failure would mean an end to American support for the system that has given Shi'ites their first taste of real power in the Sunni-dominated Arab world for centuries.

"One consequence may be a collapse of government," Khaled al-Attiya told Reuters. "I think all the Shi'ite parties are now aware of how dangerous the issue is. Bush...is still supporting the political process and the government. But I don't think that if this plan doesn't work...he can continue."

(Additional reporting by Mariam Karouny, Aseel Kami, Ahmed Rasheed, and Huda Majeed in Baghdad; Matt Spetalnick, Tabassum Zakaria, Steve Holland and Susan Cornwell in Washington)