Secretary of Defense Donald Rumsfeld says U.S. soldiers have surrounded the Iraqi city of Fallujah in an effort to crush the insurgency there after last week's slaying and mutilation of four American civilians. Secretary Rumsfeld says U.S. forces have cordoned off the Sunni Muslim town of Fallujah. He says troops have photographs of Iraqis involved in the murder and desecration of four U.S. security guards last week and have begun a systematic effort to hunt them down.

"They have been conducting raids in the city of high value targets," he said. "They have captured a number of people over the past 36-hours. The city is isolated. A number of people have resisted and been killed. It will be a methodical effort to find the individuals who were involved."

American commanders vowed to root out insurgents after Iraqis dragged the charred bodies through the streets of Fallujah, hanging two of them from a bridge. The actions caused widespread revulsion and showed the depth of anti-American sentiment in the city. The offensive against Fallujah, about 50-kilometers west of Baghdad, is targeting Sunni Muslim insurgents who have been waging a campaign of violence against coalition forces for months.

Speaking in Norfolk, Virginia, Secretary Rumsfeld says he sees no indication that the violence in Iraq would convince the Bush administration to postpone a scheduled hand-over of power to an interim Iraqi government at the end of June. Mr. Rumsfeld says there are 135,000 U.S. troops in Iraq, a number he says is unusually large because of a massive troop rotation currently in progress.

The defense secretary says U.S. military commanders in Iraq will get additional troops if they request them. "The commanders are using the excess of forces that happen to be in there because of the deployment process," he added. "They will decide what they need and they will get what they need. At the present time they have announced no change in their plans, but they could make such a request at any time."

A senior official in Washington says U.S. military commanders are developing contingency plans to send more troops to Iraq should violence that has risen in recent days continue to get worse.