An influential World Health Organization committee is sending shock waves through the scientific community with its recommendation that researchers be permitted to conduct genetic-engineering experiments with the smallpox virus.

The idea is to be able to better combat a disease that is considered a leading bioterror threat though it was publicly eradicated 25 years ago.

The WHO had previously opposed such work for fear that a "superbug" might emerge. Because the disease is so deadly, the WHO has even at times recommended destroying the world's two known smallpox stockpiles, located in secure labs at the Centers for Disease Control and Prevention in Atlanta and in the former Soviet Union.

The recommended policy shift has reignited a debate over whether such research will help or hinder bioterrorism defenses.

The World Health Assembly - the ruling body of the 192-nation WHO - would make a final decision on whether to approve the experiments, which would include splicing a "marker" gene into the smallpox virus so its spread can be better tracked in the laboratory. The WHO committee said allowing the genetic engineering experiments would speed depletion of the remaining smallpox virus stocks.

It has been U.S. policy to refrain from genetically engineering smallpox, but that would undoubtedly change if the WHO endorses such research.

"It's absolutely the right decision," said Dr. Ken Alibek, a former top scientist in the Soviet biological weapons program who said the Soviets covertly developed smallpox as a weapon in the 1980s.

Alibek, who defected to the U.S. in 1992 and now teaches at George Mason University, said it's now possible to genetically engineer smallpox to render current vaccines useless.

"The bad guys already know how to do it," Alibek said. "So why prohibit legitimate researchers to do research for protection."

Other scientist argue that such research has little value and is too risky.

"We have seen no evidence of a threat that would justify this research," says Sujatha Byravan, Executive Director of the Council for Responsible Genetics, a Boston nonprofit. "A decade ago, the WHO was planning to destroy the worlds last remaining samples. Today, it is proposing to tinker with the virus in ways that could produce an even more lethal smallpox strain. This is a devastating step backwards."

Smallpox has plagued humans for centuries, and it's believed to have killed more people than all wars and epidemics combined. Death typically follows massive hemorrhaging.

A similar debate was set off last year when researcher Mark Buller of Saint Louis University announced that he had genetically engineered a mousepox virus that was designed to evade vaccines. Buller created the superbug to figure out how to defeat it, a key goal of the government's anti-terrorism plan. He designed a two-drug cocktail that promises to defeat the exceptionally deadly virus.

Buller said similar smallpox protections could be developed if researchers were free to experiment responsibly with genetic engineering. Mousepox is a close relative of smallpox.

Buller's work improved upon research done in 2001 by Australian scientists who created a mousepox strain so powerful that it killed even those mice inoculated against the virus.

The WHO committee that made the genetic engineering recommendation is a subcommittee of the international organization's Advisory Committee on Variola Virus Research. News of its decision, in a meeting in Geneva last week, was first reported by National Public Radio.

The committee said further research should be carried out before a final decision is made.

"It will go through the bureaucratic process," WHO spokesman Dick Thompson said. "It will be a political decision."

He said the modified version of the virus would only be used in testing drugs for people who already have the virus and not for smallpox vaccines.

Today, the only smallpox vaccine available is unsafe for people with weakened immune systems, and can even seriously harm some healthy people, because it is made with a live virus called vaccinia that can spread through the body.

Smallpox is the only major disease to be successfully eradicated under a WHO-sponsored vaccination program. The last known case was in 1978.

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AP writer Sam Cage in Geneva contributed to this report.