The Pentagon said U.S. troops hunting for banned chemical and biological weapons and Scud missiles have so far come up empty. Rumsfeld said allied forces so far are "not in that business" of searching for weapons of mass destruction inside Iraq because they have been "on the ground 72 hours fighting a war."

The CIA has gathered "massive amounts of information" on weapons of mass destruction and Iraq, Rumsfeld said.

Iraq denies U.S. assertions it has any chemical or biological weapons.

Myers said war planners "have to be prepared for the worst case" - that Iraqi troops will use such weapons.

"The intelligence, surveillance and reconnaissance is focused looking for those delivery means, the best we can," Myer said.

"It's very hard to see where some of these things are stored, but the delivery means a little more obvious. And so we're going after those delivery means."