He also told a Pentagon news conference he couldn't say how long American forces would have to stay at increased levels in the effort to secure Baghdad.

Military deployments were recently extended to 15 months from 12 months. He said it was his hope to move as soon as possible back to 12-month deployments, with a year at home, and then eventually to 12-month terms with two years at home.

Gates was asked about a recent surge in violence and increased attacks on U.S. troops.

"The reason for the spike in violence is ... our troops and the Iraqi troops are going into areas where they haven't been for some time. They anticipated there would be a high level of combat," Gates said.

Asked about the prospects for leaving U.S. troops in Iraq at their current high levels, Gates said, "We'll just to have to wait and see the progress of these offensives."

Gen. Peter Pace, outgoing chairman of the Joint Chiefs of Staff, said the current U.S.-led offensive was "exactly what needs to be done." He said it "buys time for the Iraqi government. ...This is the right thing to do."