The long-awaited Baghdad security operation has begun, the top U.S. military spokesman in Iraq said Wednesday.

"It is ongoing as we speak," U.S. military spokesman Maj. Gen. William B. Caldwell said.

On Tuesday, Iraqi Prime Minister Nouri al-Maliki had complained that the crackdown on violence was taking too long to begin, but Caldwell said the
"implementation of the prime minister's plan has already begun and will be fully implemented at a later date, having all the parts and pieces that he wants."

Caldwell said portions of the plan "are already being put in place, and we'll continue to put more into place as the forces arrive and the assets become available."

The Iraqi general in charge of the security drive took over the operation headquarters on Monday, but there had been no announcement until Wednesday that the sweep was under way.

It's the third attempt to secure the violent capital in nine months.

During the State of the Union speech last month, U.S. President George W. Bush announced plans to send 21,500 extra troops to Iraq. Roughly 17,500 of those troops were to be sent to Baghdad.