"That is needless to say something we're concerned about," Rumsfeld said in a question-and-answer session with Pentagon employees.

"The teams have been trained in chain of control, really like a crime scene," he said. "They will have people with them who will validate things, they will have the ability to take pictures, and to make sure that the control over any piece of evidence is as clear as it possible can be."

"That will not stop certain countries, and certain types of people from claiming, inaccurately, that it was planted," he said.

The United States, which used allegations of weapons of mass destruction as justification for its March 20 invasion, has yet to turn up chemical, biological or nuclear weapons or hard evidence it was developing the banned weapons.

Rumsfeld said large areas of the country where suspect sites are located have only been open to US search teams for the past few days.

Even so, he said, Iraq's weapons will likely take time to find and then probably only with information from Iraqis who know where they are hidden.

SPACE.WIRE