US Defense Secretary Donald Rumsfeld said General John Abizaid, the commander of US forces in Iraq, has not asked for more troops but the Pentagon was prepared to supply them if he did.

"Are we considering it? No. But have we prepared? You bet," Rumsfeld told reporters at the Pentagon.

The Pentagon last week announced that it was delaying the return of 20,000 troops from Iraq for up to three months to maintain US force levels at 135,000 at Abizaid's request.

The Pentagon is prepared to replace those troops in three months, or increase force levels, if required, Rumsfeld said.

General Richard Myers, the chairman of the Joint Chiefs of Staff, told the Senate Armed Services Committee that units already have been identified in case they are needed.

"We have done a scrub of forces that could be available essentially immediately in the next few weeks to the next couple of months, in case we need more forces," he said.

"And we have a fairly extensive list of those forces and the support that goes with them," he said.

He said the list has been presented to Rumsfeld.

Some prominent members of Congress and former top military officials have criticized Rumsfeld for skimping on the number of troops deployed to Iraq, saying that the force has been inadquately sized to secure the country.

Abizaid asked for more troops after a surge of violence this month that swept through the Sunni town of Fallujah and Shiite areas in Baghdad and several southern cities.

Iraqi security forces, which the Pentagon had counted on to take some of the pressure off US forces, collapsed in many areas.

Military commanders are now bracing for more violence ahead of a planned handover of sovereignty to a transitional Iraqi government on June 30.

Before the war, military planners estimated that only 60,000 US troops would be needed at this point in the occupation, Myers told the senators.

"I'll tell you personally, I did not believe that number was correct, and I don't know that many of the Joint Chiefs believed that number was correct," he said. "But that was a number on a chart that I recall."

WAR.WIRE