An influential World Health Organization committee has upset some scientists 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 nearly 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 at times recommended destroying the world's known smallpox stockpiles, located in secure labs at the Centers for Disease Control and Prevention in Atlanta and in the former Soviet Union.

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 could be better tracked in the laboratory.

The WHO committee, which made its decision in a meeting in Geneva last week, said that inserting the marker gene would not make the disease any more dangerous and that allowing such experimentation would speed depletion of the remaining smallpox virus stocks.

"It's absolutely the right decision," said Ken Alibek, a bioterrorism expert at George Mason University. Alibek said it is 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?"