WASHINGTON -- Iraqi scientists know how to make chemical weapons that can penetrate military protective clothing, and Iraq imported up to 25 metric tons last month of a powder crucial to making such "dusty" weapons.

Iraq told the United Nations the powder was destined for a pharmaceutical company that a former weapons inspector says was ordered by President Saddam Hussein before the 1991 Gulf War to work on chemical and biological weapons.

The powder, sold under the brand name Aerosil, has particles so small that, when coated with deadly poisons, can pass through the tiniest gaps in protective suits.

Experts inside and outside the U.S. government say they aren'tt certain Iraq has dusty chemical weapons. Declassified U.S. intelligence documents say Iraq produced a dusty form of the blister agent mustard gas in the 1980s and used it during its eight-year war with Iran.

If Iraq made and used a powdered form of its deadliest nerve agent, VX, it could kill U.S. troops dressed in full protective gear, according to a 1990 Defense Intelligence Agency assessment. Although the military's protective suits have been improved since then, experts say dusty weapons could penetrate the new suits.

Pentagon officials refused to discuss the permeability of the new suits or whether Iraq has weapons that could pass through them. Such information is classified, they said.

Toxic danger

The researcher, Eric Croddy of the private Center for Nonproliferation Studies, said dusty VX would be a serious danger to U.S. troops. VX is so toxic that, in its liquid form, a drop on the skin can kill within minutes.

"The effects of dusty VX, depending on how it gets in the body, would be somewhat faster," Croddy said. "It's certainly much more injurious and much more of a severe threat."

Dusty chemical weapons are formed by mixing a liquid chemical agent with a fine powder to coat the powder's tiny particles with the deadly poison. The particles' small size allows them to pass through the fabric of a protective suit and any tiny gaps around the seal of a gas mask.

The latest U.S. military protective suits have a layer of charcoal in the fabric to trap any poisons that might penetrate the outer covering, but particles small enough could pass through the charcoal layer.

"The closest analogy is, no matter what happens when you go to the beach, you still get sand in your shorts," Croddy said.

The poisonous powder also would settle in the tiniest nooks and crannies of buildings and equipment, making decontamination difficult.

Even if dusty chemical weapons caused no U.S. casualties, they could force American soldiers to work in clumsy protective gear, decontaminate their equipment and avoid contaminated areas, giving Iraqi soldiers time for defenses.

U.S. intelligence reports before the Gulf War said Iraq was capable of making dusty VX. The reports said no evidence was found that Iraq had made dusty VX, and U.N. inspectors were unable to find any hard evidence of that.

In September, The New York Times quoted an Iraqi defector as saying Saddam's weapons scientists secretly began producing dusty VX as early as 1994.