WASHINGTON -- The United States is "prepared and concerned" about possible Iraq-sponsored terrorist attacks if President Bush orders a war to disarm Saddam Hussein, Defense Secretary Donald H. Rumsfeld said Thursday.

Rumsfeld also said the Iraqi leader could launch chemical or biological attacks on U.S. troops.

"There is a danger that Saddam Hussein would do things he's done previously. He has in the past used chemical weapons," Rumsfeld said on a call-in show on Infinity Broadcasting and National Public Radio stations. "One has to be prepared and concerned that could occur.

"I have no doubt that if he's able, he would like to see that terrorist attacks occur in the event that military action was taken."

If the United States uses military force to oust Saddam, Rumsfeld said, there would be a military command in Iraq while authorities tried to track down all of Iraq's weapons of mass destruction -- a task Rumsfeld earlier said could take many months. Then some sort of interim government of Iraqis should take control, Rumsfeld said.

Iraq probably would not be able to fight for very long after a U.S.-led invasion, Rumsfeld said, noting that ground combat in the 1991 Persian Gulf War lasted just 100 hours.

"I can't say if the use of force would last five days or five weeks or five months, but it certainly isn't going to last any longer than that," Rumsfeld said.

He rejected Saddam's claims that Iraq has no chemical, biological or nuclear weapons programs.

"We know that Saddam Hussein has chemical and biological weapons, and we know he has an active program for development of nuclear weapons," Rumsfeld said.