Defense Secretary Donald Rumsfeld is disputing suggestions that U.S. air power alone would be sufficient to destroy Iraq's chemical, biological and nuclear weapons sites.

Mr. Rumsfeld says many of Iraq's facilities for so-called weapons of mass destruction are deeply buried and would be difficult to eliminate with air power alone.

Speaking during a visit to the U.S. Joint Forces Command in Suffolk, Virginia, south of Washington, Mr. Rumsfeld also says Iraq has benefited from information on concealment tactics from American spies who defected to the Soviet Union and Russia.

He gave no elaboration. But he says that in addition to buried facilities, some of Iraq's weapons of mass destruction are contained in mobile trailers. He told a reporter, that makes such targets difficult to hit from the air.

"A biological laboratory can be on wheels in a trailer and make a lot of bad stuff and it's moveable and it looks like most any other trailer," he said. "So the idea that it's easy to simply go do what you suggested ought to be done from the air, the implication being from the air, is a misunderstanding of the situation."

During his exchange with reporters, Mr. Rumsfeld also disputed a new published report claiming that many U.S. commanders favor a continued policy of containing Iraq rather than unleashing an offensive aimed at removing Iraqi leader Saddam Hussein from power.

Other recent reports have purported to lay out the broad plans for possible U.S. military action, including one for a massive invasion involving a quarter-million troops.

Such reports have angered Mr. Rumsfeld, who has ordered an investigation into the possible leak of secret information.

Mr. Rumsfeld says Iraq continues to pose a danger with its chemical and biological weapons programs and what he terms its enormous appetite for nuclear weapons.