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 that is a crucial ingredient to 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 Persian 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, they can pass through the tiniest gaps in protective suits.

Experts inside and outside the U.S. government say they are not certain Iraq has dusty chemical weapons. Declassified U.S. intelligence documents say Iraq produced a dusty form of the blister agent mustard 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.

The 1990 DIA document said soldiers could protect themselves by throwing rain ponchos over their chemical suits, which would reduce the fatality risk to near zero. One expert wrote later: “One gets the sense that this was recommended in the face of few other options.”

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.”