U.S. tribal allies in Iraq angry over airstrikes

Simmons said the number of improvised explosive device events across Iraq were 1,560 in October, compared with 3,239 in March. "Events" refers to bombs which either detonated or were found before they went off.

Car bombs have been more difficult to stop. In the northern oil-producing city of Kirkuk, a car bomb targeting a police convoy killed six people, including one policeman, police said. They said 17 people, including children on their way to school, were wounded.

While security has improved, Iraq's leaders have made little progress at the national level in healing deep divisions between majority Shi'ites and minority Sunni Arabs who were dominant under Saddam Hussein.

U.S. Ambassador Ryan Crocker said on Thursday he hoped parliament would soon pass a draft law that would ease curbs on former members of Saddam's Baath party joining the civil service and military. The government said on Wednesday it had presented the bill to parliament.

(Additional reporting by Dean Yates and Missy Ryan in Baghdad; editing by Elizabeth Piper)