Britain announced today that it would join the United States in inoculating troops in the Persian Gulf against biological weapons.

The British Defense Ministry said it was ordering protective measures including the provision of respirators and special clothing and "a program of inoculation and provision of antibiotics and antitoxins."

The British announcement came as the Pentagon publicly confirmed that it planned to begin vaccinating American troops soon. Pentagon spokesmen today declined to say precisely what vaccines would be given or how many soldiers would be inoculated.

But Dr. Kenneth L. Wilcox, the deputy director of the Michigan Department of Public Health, said in an interview today that his agency had increased the production of a vaccine for anthrax, and was continuing to expand the production, in response to a request from the Army.

Called the Only Producer

Dr. Wilcox said the department was the only institution in the United States that made the vaccine.

Government officials familar with classified intelligence reports said Washington was concerned by Iraq's ability to use anthrax as a biological weapon.

Dr. George French of the Salk Institute for Biological Studies said his organization had received a request from the Army two weeks ago to manufacture a vaccine to counteract botulism. The vaccine is made at a laboratory in Swift Water, Pa.

Delbert Glanz, a vice president at the Salk Insitute, said it would "take some time" before a large quantity of that vaccine could be produced, since the program was just getting under way.

Details of the Pentagon's vaccination plan remain secret. A Pentagon spokesman said today that no officials were available to give interviews on the program and refused to discuss key aspects of the program.

Not Enough Vaccine

The program is politically sensitive because officials say the United States does not now have enouch vaccine to protect all servicemen and women in the Persian Gulf -- let alone to protect allied forces and Saudi citizens.

The Pentagon has not said when it might have enough vaccine for all American forces or fully explained how allies are to be protected. Nor has it explained how long it will take for the vaccinations to provide the American troops with full immunity against Iraqi biological weapons.

Dr. Wilcox said the anthrax vaccine was customarily given in two or three shots a couple of weeks apart.

"The immunity gradually increases as the time goes along," he said.

Some experts on chemical and biological weapons complained today that the Pentagon did not appear to be sufficiently prepared to deal with the problem of biological weapons.

Pentagon Is Criticized

Elisa D. Harris, a specialist at the Brookings Institution, questioned why the Pentagon did not yet have enough vaccine available to inoculate all the American troops and why it had not vaccinated the troops earlier.

"Given that we have been aware of Iraq's effort to develop biological weapons for a considerable period of time, the Pentagon should have had effective contingency plans for procuring adequate supplies of the vaccine before now and for carrying out a prompt vaccination program," Ms. Harris said.

Pentagon spokesmen declined to respond to this criticism, saying they could not go beyond the official statement today that a program of inoculations was to begin soon. But a Pentagon official, who spoke only on the condition that he not be identified, asserted that the criticism was misplaced.

"Very few places are equipped to make this stuff," the official said. "It is difficult to ramp up production, but we started that early on."

Flotilla Sets Sail

Although Pentagon officials said on Thursday that the vaccination program would begin in a matter of weeks, an official said today that the inoculations would begin much sooner, perhaps as soon as next week.

The confirmation of the vaccination program came as the a large Navy flotilla set sail for the gulf. Two aircraft carrier battle groups, a 17-ship armada carrying 16,000 sailors and marines, left from several ports.

The aircraft carriers America and Theodore Roosevelt and various support ships left from Norfolk Naval Base in Virginia. Other vessels in the battle group left from Mayport, Fla., and New York City.

The ships are to be in the gulf by mid-January, and the United States will then have six aircraft carriers in the region. It will be the first time since the Korean War that the Navy has deployed six carriers in a single military operation. Each carries about 80 planes, about 30 of which are designed to attack targets on land. 

American military personnel in front-line positions in Saudi Arabia will be adequately protected against all but the heaviest doses of Iraqi biological warfare agents in the event of war, an Army expert says.

The officer, Col. Ronald G. Williams, commander of the Army's Medical Research Institute of Infectious Diseases at Fort Detrick, Md., said his command had been "forced to assume" that Iraq could attack American troops with a range of biological agents.

"We know that they have manufactured and used chemical weapons in Iran and Kurdistan, and that they therefore could produce and use biological agents as well," he said in a recent telephone interview from Fort Detrick.

Colonel Williams's command is responsible for developing protective techniques, vaccines and antitoxins for American troops against all disease-causing agents, including bacteria, viruses, funguses and toxins.

One of the main military concerns is anthrax, a potentially lethal disease that can infect most animals, including humans. The most dangerous form of the disease, pulmonary anthrax, can be spread through the air in the form of microscopic spores, and Iraq is believed to have sufficient supplies of anthrax to infect a large area. Anthrax can be spread by explosive shells, bombs or rockets. Three Types of Defense

Colonel Williams said protection against anthrax comprises three basic defenses: protective clothing and masks, which are also used against chemical agents, vaccination and antibiotic therapy.

The anthrax vaccine available to American forces, prepared from killed anthrax bacteria, is effective against the major known forms of the disease, Colonel Williams said. But he warned, "If a vaccinated person were exposed to an overwhelemingly large dose, the protection might not be effective."

The anthrax immunization procedure for American forces consists of an initial injection followed by two booster injections, one after two weeks and the second after four weeks. Troops receiving their initial injections now will not be fully immunized until their final booster injections nearly a month from now, by which time war may have begun. Production of anthrax vaccine has been increased, Colonel Williams said, but supplies will remain limited to "units at the greatest risk" for the time being.

Even if a soldier were to contract anthrax, military authorities believe that antibiotic therapy will be effective. But Colonel Williams and other experts fear that Iraqi bacteriologists may be capable of developing anthrax strains resistant to antibiotics, a possibility that would greatly increase the vulnerability of American troops.

Some of the biological-warfare diseases that Iraq might disseminate, including anthrax, are endemic in many parts of the world, including Saudi Arabia. The public health authorities have developed many strategies for fighting these diseases. The first anthrax vaccine was developed by Louis Pasteur more than a century ago.

But the genes of disease-causing organisms can be altered by nature or human beings. Genetic changes can produce diseases that defeat existing public health strategies, and when this happens, devastating epidemics can result. American experts hope that even during a crisis, Iraq will not be tempted to resort to germ warfare.

Iraq is believed to have developed a range of different biological agents, including organisms that cause cholera and typhoid, as well as potent biological toxins, including botulin toxin and rycin. Rycin, derived from castor beans, has been used by Bulgarian secret agents for assassinations. Some Vaccines Listed

Colonel Williams declined to comment on subjects that might compromise "intelligence or operational" secrets, including Washington's assessment of Iraq's biological arsenal. But he said his command had developed vaccines against tularemia, Rift Valley fever, Q fever, several forms of hemorrhagic fever and a variety of toxins.

Toxins are especially lethal when used to contaminate water supplies. Dr. Raymond A. Zilinskas of the Maryland Biotechnical Institute said in a 1989 report to the American Association for the Advancement of Science that one pound of toxin produced by the salmonella bacteria that cause typhoid could poison a 1.32-million gallon reservoir enough to kill anyone taking a drink. It would take 5 tons of nerve gas or 10 tons of potassium cyanide to achieve the same result, he said.

Iraq is believed to have manufactured large quantities of botulin toxin. Colonel Williams said that his research group had developed an experimental vaccine against botulin, and that the drug had been used on laboratory workers. It apparently protects them against accidental poisoning by the toxin, he said. As an experimental drug, however, the vaccine is not likely to be available in large amounts.

Nevertheless, the Pentagon plans to inoculate at least some of the servicemen and women serving in the Persian Gulf region with the botulin vaccine. On Dec. 21 the Defense Department obtained a special waiver enabling the military authorities to inoculate troops with the experimental drug, even without their informed consent.