Some U.S. troops serving with Operation Desert Shield soon will be vaccinated against potential Iraqi germ weapons, the Defense Department announced yesterday.

Officials said the Pentagon's decision to order the vaccinations is the latest step in continuing preparations for armed conflict and reflects a desire by military commanders to protect U.S. forces in Saudi Arabia against all types of weapons Iraqi troops are known to have.

"We are committed to providing maximum protection for our troops, including against chemical and biological weapons," a Pentagon spokesman said in a brief prepared statement. "We expect to begin a program of inoculations soon."

A similar program of inoculations against germ warfare, backed up by the "provision of antibiotics and antitoxins," was announced by Britain's Defense Ministry in London.

The U.S. announcement comes two months after Director of Central Intelligence William H. Webster revealed in a Washington speech that Iraq had germ weapons. House Armed Services Committee Chairman Les Aspin (D-Wis.) later said intelligence analysts believed Iraqi President Saddam Hussein's forces would be able to deliver a significant quantity of lethal germs in combat after Jan. 1.

However, U.S. military and intelligence officials have said they do not believe an Iraqi attack with biological weapons is likely because it would cause worldwide revulsion and lead to an all-out attack against Iraq by U.S. conventional forces.

Webster, asked in a Dec. 14 interview with The Washington Post if U.S. troops could expect such an attack, said, "I think 'expect' is not the exact word. . . . We have to prepare for that possibility."

Other U.S. officials said the Pentagon's decision was not based on any new intelligence information but was influenced by the need to administer the vaccine in separate doses stretching over several weeks before it produces sufficient antibodies against disease. The administration has said conflict might occur after Jan. 15 if Iraq does not withdraw from Kuwait by then, as mandated by the United Nations.

Webster said an Iraqi germ weapon attack was considered less likely than an attack involving one of the deadly poison gases known to be in Iraqi hands because germ weapons do not cause immediate deaths while the poison gases can kill almost instantaneously.

"As a tactical weapon, it is not of very much value," Webster said of germ agents. "It would be of value as a terror weapon."

Defense officials yesterday declined to say what germs they suspected Saddam would use, how many personnel would receive inoculations or when the shots would begin. But U.S. analysts said the administration is primarily concerned about potential Iraqi use of anthrax, a persistent, natural disease-causing agent that was honed as a potential weapon by the British during World War II.

The only known U.S. manufacturer of a vaccine against anthrax is Michigan's Department of Public Health, which produces roughly 1,000 doses annually for academic research and an unknown quantity for the Defense Department. Kenneth Wilcox, the Michigan agency's deputy director, said yesterday that "we are in the process of increasing production" of the vaccine under a recent Defense Department contract.

But he declined to say how much it had produced for the Pentagon under previous contracts over what he termed a "five- to 10-year period." He said the government considers the number too sensitive to disclose. Officials in Washington yesterday confirmed a report in The New York Times that not enough dosages are available to vaccinate all U.S. and allied personnel who might exposed to the agents.

Officials at a division of the Salk Institute in Sweetwater, Pa., disclosed yesterday that they were recently ordered to manufacture a large supply of vaccine against a form of botulism, another natural disease-causing agent long considered a top candidate for germ warfare.

The purpose, one knowledgeable source said, "is to replace a {previous} order {for the botulinum vaccine} that will be expended in Operation Desert Shield." Officials again declined to say how many dosages of the vaccine are available.

Harvard biochemist Matthew Meselson, an authority on biological and chemical warfare, said of the Pentagon's new vaccination order, "I wouldn't consider it alarming." He said germ weapons "take quite an effort" to use effectively because of the difficulties associated with safely producing the spores and dispersing them in a concentrated aerosol close to enemy troops.

Meselson said that vaccines were "at the end of a long line" of protective measures available to U.S. soldiers in the region. These measures include protective masks and suits to prevent contact with the spores and, in the case of anthrax, the use of oral penicillin immediately after an attack.

Iraq also would have to take steps to protect its troops against infection, possibly including equipping them with suits and masks or administering vaccine. One intelligence expert said that while "the majority of Iraqi troops" evidently are equipped with such suits, there did not appear to have been any Iraqi attempts at mass vaccination.