When Indonesia's health minister stopped sending bird flu viruses to a research laboratory in the U.S. for fear Washington could use them to make biological weapons, Defense Secretary Robert Gates laughed and called it "the nuttiest thing" he'd ever heard.

Yet deep inside an 86-page supplement to United States export regulations is a single sentence that bars U.S. exports of vaccines for avian bird flu and dozens of other viruses to five countries designated "state sponsors of terrorism."

The reason: Fear that they will be used for biological warfare.

Under this little-known policy, North Korea, Iran, Cuba, Syria and Sudan may not get the vaccines unless they apply for special export licenses, which would be given or refused according to the discretion and timing of the U.S. Three of those nations — Iran, Cuba and Sudan — also are subject to a ban on all human pandemic influenza vaccines as part of a general U.S. embargo.

The regulations, which cover vaccines for everything from Dengue fever to the Ebola virus, have raised concern within the medical and scientific communities. Although they were quietly put in place more than a decade ago, they could now be more relevant because of recent concerns about bird flu. Officials from the U.S. Department of Health and Human Services and the Centers for Disease Control and Prevention said they were not even aware of the policies until contacted by The Associated Press last month and privately expressed alarm.

They make "no scientific sense," said Peter Palese, chairman of the microbiology department at Mount Sinai School of Medicine in New York. He said the bird flu vaccine, for example, can be used to contain outbreaks in poultry before they mutate to a form spread more easily between people.

"The more vaccines out there, the better," he said. "It's a matter of protecting ourselves, really, so the bird flu virus doesn't take hold in these countries and spread."

U.S. Commerce Assistant Secretary Christopher Wall declined to elaborate on the precise threat posed by vaccines for chickens infected with avian influenza, except to say there are "valid security concerns" that they "do not fall into the wrong hands."

"Legitimate public health and scientific research is not adversely affected by these controls," he said.

But some experts say the idea of using vaccines for bioweapons is far-fetched, and that in a health emergency, it is unclear how quickly authorities could cut through the current red tape to get the vaccines distributed.

Under normal circumstances it would take at least six weeks to approve export licenses for any vaccine on the list, said Thomas Monath, who formerly headed a CIA advisory group on ways to counter biological attacks. All such decisions would follow negotiations at a "very high level" of government.

That could make it harder to contain an outbreak of bird flu among chickens in, say, North Korea, which is in the region hardest hit by the virus. Sudan and Iran already have recorded cases of the virus in poultry and Syria is surrounded by affected countries. Cuba, like all nations, is vulnerable because the disease is delivered by migratory birds.

Kumanan Wilson, whose research at the University of Toronto focuses on policymaking in areas of health protection, said it would be ironic if the bird flu virus morphed into a more dangerous form in one of those countries.

"That would pose a much graver threat to the public than the theoretical risk that the vaccine could be used for biological warfare," he said.

The danger of biological warfare use depends on the specific virus or bacteria. But most experts agree that bird flu vaccines cannot be genetically altered to create weapons because they contain an inactivated virus that cannot be resuscitated.

It's also unlikely they would be used to create a resistant strain of the virus as part of efforts to wreak havoc within global poultry stocks. If enemy states wanted to do that, they could make their own vaccines or turn to a less hostile country like China, said Ian Ramshaw, an expert on vaccine immunology and biosecurity at The Australian National University in Canberra.

"I can think of no scientific reason how a terrorist organization could use such a vaccine for malicious intent," he said. "I personally think it's a rather silly attitude and the U.S. is probably going overboard as it has in the past with many of its bioterrorism initiatives."

Meanwhile, bioethicists say limiting vaccines could also raise moral questions of whether some countries should be denied because of decisions based on foreign policy. They said the export controls appear inconsistent, as Libya, Iraq and two dozen other countries suspected by the U.S. of having biological weapons programs do not face restrictions on the export of poultry vaccines.

"If there really is a serious threat, to be consistent we'd have to more heavily regulate who has access to the vaccine," said Michael Selgelid, who co-authored the book "Ethical and Philosophical Consideration of the Dual Use Dilemma in the Biological Sciences."

"There are malevolent actors in the U.S. just like there might be in all these other countries," he said.

The policies were initially put in place amid biosecurity fears in the mid-1990s and then bolstered after the Sept. 11, 2001 attacks and subsequent anthrax letter mailings. The vaccines are among a long list of other items barred to rogue states over fears they could be used to make weapons of mass destruction, from technology and chemicals to dangerous pathogens.

Bird flu has killed more than 240 people across the world since 2003, nearly half of them in Indonesia.

Indonesia's health minister Siti Fadilah Supari first drew widespread attention when she boycotted the World Health Organization's 50-year-old virus sharing system last year, saying pharmaceutical companies were using viruses from developing nations without their knowledge to make expensive vaccines. She has since called for the creation of a global stockpile of drugs or other forms of benefit-sharing.

Dr C