Captured Iraqis have given U.S. interrogators information about possible chemical and biological weapons sites, the commander of American ground troops in Iraq said Friday.

Lt. Gen. David McKiernan (search) said he's confident there are biological and chemical weapons still hidden in Iraq. No such weapons have been found, although President Bush said he ordered the war to eliminate what he said were Iraq's weapons of mass destruction (search).

Information on chemical and biological weapons is rare because so few Iraqis were involved in those programs, McKiernan told Pentagon reporters over a video link from Baghdad. Questioning of some Iraqi officials has been fruitful, however, he said.

"From some interrogations, we get information that leads us to another source, that we have to go locate certain facilities and go in there and check those out," McKiernan said. "I'm not going to go into the details, but there is discussion from both the chemical and the biological side that leads us to intelligence that we have to go confirm or deny."

The failure to find any banned weapons in Iraq has prompted critics in the United States and abroad to question whether Bush overstated the evidence that Saddam Hussein's regime had them. McKiernan said he had no such doubts.

"Even if there were no interrogations, I would tell you personally, I think there's a lot still hidden that it will take time for us to uncover," McKiernan said.

The general said the attacks against U.S. troops in Iraq do not appear to be coordinated by any central authority. A prominent former Iraqi exile, Ahmed Chalabi of the Iraqi National Congress (search), said this week that Saddam was still alive and offering bounties for the killing of American troops.

McKiernan said the attacks were "only coordinated locally, not nationally."

Still, "there is the probability that there are financial trails that lead to other parts of Iraq and there might be communications that go to other parts," McKiernan said. He didn't elaborate.

McKiernan said many of the attacks were from former members of Saddam's Baath Party (search), his intelligence services or Special Republican Guard.

American troops will begin to leave Iraq "when the time is right," McKiernan said, though he would not predict when that would be. Some units, such as the Army's 3rd Infantry Division, have been in Iraq for nearly three months after spending nearly a year preparing for the invasion in Kuwait.

"I'm not worried about our units and our soldiers losing their combat edge," McKiernan said, adding that some equipment had to be repaired or replaced.