Secretary of Defense William Cohen has made the potential use of biological or chemical agents by terrorist groups or individuals his personal signature contribution to the national security debate in the past several years.

In a Nov. 26, 1997, op-ed article, "In the Age of Terror Weapons," he wrote:

"Terrorist groups and even religious cults will seek to wield disproportionate power by acquiring and using these weapons that can produce major casualties."

"We should expect more countries and terrorist groups to seek -- and to use -- such weapons."

"We have begun to treat the threat of chemical and biological weapons as a likely -- and early -- condition of warfare."

"Most ominous among these threats is the movement of the front line of the chemical and biological battlefield from foreign soil to the American homeland."

Nothing supports these propositions. They are exaggerated and alarmist. They are probably even dangerous and counterproductive, since they virtually solicit and induce precisely what they portray as fearing. They trumpet a perception of U.S. national vulnerability to chemical and biological weapons, whether or not that is actually the case. They therefore are likely to stimulate the interest of other states and terrorists in such weapons.

No agency of the U.S. government has prepared a threat analysis that provides indications that these events are imminent or even likely. Instead, various analysts have provided vulnerability projections and scenarios, which are always easy to concoct in the abstract. Vulnerability can neither be denied nor disproved.

In his most recent contribution in your paper ["Preparing for a Grave New World," op-ed, July 26], Cohen wrote:

"Also looming is the chance that these terror weapons will find their way into the hands of individuals and independent groups -- fanatical terrorists and religious zealots beyond our borders, brooding loners and self-proclaimed apocalyptic prophets at home."

It is possible that Cohen offers these fantasies in response to the first concerted expressions of expert opinion in recent months, in conferences and publications, which argue that the past years have seen exaggeration on this subject approaching hysteria.

Cohen referred to the Japanese Aum Shinrikyo group, whose 1995 use of the chemical nerve agent Sarin in the Tokyo subway killed a dozen people and injured several thousand. It was subsequently learned that this same group had made a substantial effort to produce biological weapons as well, and this event released the flood of fearsome scenarios and projections regarding chemical and biological terrorism. The quality of the Sarin produced by the Aum group was poor. Nevertheless, the group's efforts to produce a chemical weapon could be considered a qualified success. Insofar as biological agents are concerned, however, their efforts were an absolute failure.

The group had unlimited funds to procure whatever equipment was necessary. They had a small group of trained professional scientists in their organization. They had four years in which to work, undisturbed. They attempted to produce two agents -- anthrax and botulinum toxin -- both usually considered relatively simple to work with.

Nevertheless, they failed to produce any agent.

Either the advice reaching the secretary of defense and other senior officials on this subject is extraordinarily poor, or they are intentionally disregarding real-world experience. The portrayal of this subject by senior government officials is grossly exaggerated, and the government's policy is accordingly based either on faulty assessments or no assessment at all.

-- Milton Leitenberg

The writer is a senior fellow at the

Center for International and Security Studies

at the University of Maryland.