WASHINGTON — The government stands to waste $100 million a year if two federal agencies cannot agree to coordinate the use of a vaccine for the deadly anthrax bacterial disease.

The departments of Defense and Health and Human Services each purchase the anthrax vaccine, BioThrax. But much of the vaccine purchased for HHS goes unused, according to government investigators.

Currently the Strategic National Stockpile has more than 520,000 doses of the vaccine — worth $12 million — that have already expired, according to a Government Accountability Office report obtained by The Associated Press before its release at a hearing Tuesday before the Senate homeland security committee.

GAO said the two departments should create a single inventory system for these drugs so they are not wasted. The Defense Department gives BioThrax to personnel who will deploy to Iraq, Afghanistan and the Korean peninsula, according to the report.

The national stockpile is kept in secret storage facilities around the country. As of June, the stockpile had about 10 million doses of the vaccine — all of which will expire if not used.

"It just seems like a common-sense solution to a problem that otherwise is going to cost the taxpayers hundreds of millions of dollars," Sen. Susan Collins, R-Maine, said Tuesday. Collins is the top Republican on the committee.

The departments say legal issues stand in the way of a vaccine-sharing agreement, and say the GAO overestimated the amount of money lost as a result.

Responding to the report, an HHS official said such an agreement could save $25 million a year rather than $100 million. Another obstacle to such an agreement is that the Pentagon does not use nearly as many vaccines as HHS buys for its stockpile, said David G. Jarrett, the defense department's medical director at the office of the special assistant for chemical and biological defense and chemical demilitarization programs.

"It should also be noted that DoD cannot distribute expiring stocks at the last minute," Jarrett wrote in his response to the report.

In September and October 2001, anthrax exposures in the U.S. killed five people and injured 22. The federal government accelerated its program to develop more successful vaccines, but that program continues to run into problems. Investigators have not determined who is responsible for the attacks.

"This keeps me and a lot of other people up at night," Sen. Joseph I. Lieberman, I-Conn., said Tuesday. Lieberman chairs the Senate committee and said this would be the first of many reports on anthrax and bioterrorism. "The ease of bringing biological agents into the country or actually procuring them here and then the propensity they have to multiply and spread has devastating consequences."

The vaccine's shelf life is currently three years, according to manufacturer Emergent BioSolutions Inc. In September the company signed a three-year contract with HHS to provide 18.75 million doses of the anthrax vaccine for the national stockpile.

HHS plans to use the expired anthrax vaccines even though that goes against Food and Drug Administration guidelines, according to the report. But in its response to the report, HHS said it would destroy the expired drugs.