Iraqi police reported a dozen civilians killed in an airstrike in the same area. But the military said those killed in the raid were insurgents, including six who had shaved their bodies apparently in preparation for suicide operations.

A police commander was shot to death along with his driver in Balad Ruz, 45 miles northeast of Baghdad.

A roadside bomb near the northern city of Tuz Khormato killed four Iraqi soldiers, including an officer.

The violence was reported by police officials who declined to be identified because they weren't supposed to release the information.

Last year, the U.S. military deaths spiked as U.S. troops sought to regain control of Baghdad and surrounding areas.

The death toll has seesawed since, with 2007 ending as the deadliest year for American troops at 901 deaths. That was 51 more deaths than 2004, the second deadliest year for U.S. soldiers.

The 4,000 figure is according to an Associated Press count that includes eight civilians who worked for the Department of Defense.