Battles also erupted between Shi'ite militias and U.S. forces in towns and cities in southern Iraq, unrest that threatens to open a new front in the U.S. led Iraqi occupation less than 90 days before sovereignty（主权）is set to be handed back to the Iraq people.

U.S. forces also began an operation Tuesday - code named Vigilant Resolve - in the town of Fallujah west of Baghdad. This American was among the columns of Marines involved in sealing off the Sunni stronghold as part of the hunt for those responsible for the deaths of four American civilians a week ago.

"We're going to find these terrorists and we're going to take care of the problem."

Defense Secretary Donald Rumsfeld confirmed the raid was under way, telling reporters the Marines know who they are looking for and that a number of people resisting arrest have already been killed.

"They have photographs of a good many people who were involved in the attacks against the individuals and they have been conducting raids（袭击，搜捕）in the city against high value targets. They've captured a number of people."

U.S. military commanders are now considering whether to ask for more troops to help put down what has been some of the worst violence across Iraq since the end of major combat operations nearly a year ago. And even though President Bush is sticking to the date of June 30 for returning sovereignty to the Iraqi people, others in Washington are beginning to question whether that date can hold if the current level of violence continues.