U.S.-trained Iraqi police appear to have coordinated some of the attacks on U.S. or Iraqi targets, the top U.S. military official in Iraq said Saturday.

U.S. military officials are concerned that a few of the numerous Iraqi civilians hired by the U.S. military may have planned attacks by gleaning intelligence on troop movements and travels of high-ranking officers, Lt. Gen. Ricardo Sanchez (search) told reporters at the Baghdad Convention Center.

"Clearly those are concerns we have. We try to do the vetting (of Iraqi employees) as close as we can," he said. "There have been instances when police were coordinating attacks against the coalition and against the people."

Sanchez also said there is no evidence that Al Qaeda terrorists have taken part in the long string of attacks on U.S. and Iraqi targets.

He said the insurgency was becoming particularly bloody for Iraqi civilians. Guerrillas launched more than 150 attacks on Iraqi civilian and police targets, killing scores during the Muslim holy month of Ramadan (search), which ended last week.

Sanchez also said the United States is boosting the number of infantrymen in Iraq and moving from a force based on tanks and heavy armored vehicles to one specializing in urban raids.

A new phase in the Iraq war, known as Iraqi Freedom II (search), would begin as current forces are rotated out of Iraq and replaced by new units, including several thousand U.S. Marines, Sanchez said.

"We are going to change the composition of our forces," Sanchez said. "We'll have more infantry. We're moving to a more mobile force, one that has the right blend of light and heavy."

Sanchez said he saw no need for an overall increase in U.S. forces in Iraq, and the number of troops would decrease as transportation, logistics and communications personnel are sent home.

The general said some support troops are being replaced by civilian contractors, in the case of transportation and logistics. The military also is starting to use commercial sources for communications, he said, thus allowing more soldiers to depart.

Washington currently has 130,000 troops in Iraq.

The Department of Defense had announced this month that the total number of U.S. troops in Iraq would drop to about 105,000 after troop rotations that start in January are completed in May. But the additional marines appear to bump up that total to 110,000.

"There's no way we're going to put this mission at risk in terms of combat power," Sanchez said, explaining the need for the marines, whose normal tasks tend toward invasions, not occupation duties.

"What we're in search of is a very mobile, very flexible, lethal force that can accomplish its mission. Those terms are dictated by the enemy."

The Associated Press contributed to this report.