A long-awaited U.S. and Iraqi security operation in Baghdad is under way to curb attacks that have killed hundreds in the capital.
U.S. Major General William Caldwell says the crackdown will be expanded as more forces arrive in Baghdad. The plan calls for 90-thousand Iraqi and American troops to operate in Baghdad.
U.S. Defense Secretary Robert Gates, testifying on Capitol Hill, said Wednesday the operation is not the last chance for the United States to beat insurgents in Baghdad.
Meanwhile, the U.S. military says it is investigating the crash of a Marine transport helicopter in al-Anbar province Wednesday that killed all seven personnel aboard.
An al-Qaida-linked Sunni insurgent group says, in an Internet posting, that it shot down the helicopter. It was the fifth U.S. helicopter to crash in recent weeks in Iraq.
In other developments, at least three security guards at a building holding Iraqiya state television were shot and killed Wednesday.
And the U.S. military says a Marine was killed Tuesday in combat in al-Anbar province.