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 virus.

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. The report is to be the subject of 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.

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.

"We have an awful lot to do in the area of medical readiness and to me, the results of the government's efforts to protect Americans through countermeasures and new technologies are mixed," Sen. Joe Lieberman, I-Conn., said in a statement. Lieberman is chairman of the Senate Homeland Security and Government Affairs Committee.

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.

"HHS must learn the lessons from past failures so that we can improve our preparedness for a possible terrorist attack using biological weapons," Sen. Susan Collins, R-Maine, said in a statement Monday. Collins is the top Republican on the Senate committee.