GENEVA - Health ministers from around the world agreed Tuesday to put off setting a deadline to destroy the last known stockpiles of the smallpox virus for three more years, rejecting a US plan that had called for a five-year delay.

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After two days of heated debate, the 193-nation World Health Assembly agreed by consensus to a compromise that calls for another review in 2014.

The United States had proposed a five-year extension to destroying the US and Russian stockpiles, arguing that more research is needed and the stockpiles could help prevent one of the world's deadliest diseases from being used as a biological weapon.

But opponents at the decision-making assembly of the World Health Organization said they saw little reason to retain the stockpiles, and objected to the delay in destroying them.

Dr Nils Daulaire, head of the US Office of Global Health Affairs and the chief American delegate to the assembly, expressed some disappointment but said the compromise was satisfactory.

"We were disappointed that despite the fact that we had extremely strong support for a resolution that would have even more strongly endorsed the program of research and that a majority of that support came from the global south, that Iran almost unilaterally blocked that," he said. "We could have won a vote if we had chosen to go that route, but it was not the way we view the well-being of both WHO processes and global health."

The assembly, like the UN General Assembly, is a world forum whose decisions aren't legally binding. It declared smallpox officially eradicated in 1980, and the UN health agency has been discussing whether to destroy the virus since 1986.

Then in 2007, the health assembly asked WHO's director-general to oversee a major review of the situation so that the 2011 assembly could agree on when to destroy the last known stockpiles.

Daulaire said the US would act in accordance with the decisions made by the assembly.

"We're very committed to consensus decisions at WHO," he said. "We believe even more strongly that WHO is a very important institution and that it has moral force and that maintaining consensus and acting on the basis of that consensus is critical for global public health."

WHO officials said in a statement that the assembly "strongly reaffirmed the decision of previous assemblies that the remaining stock of smallpox (variola) virus should be destroyed when crucial research based on the virus has been completed."