Is Iran closer to a nuclear weapon???

Despite the Stuxnet virus, are they still making progress???

Leading American scientists Friday warned against Western complacency over Iran's nuclear drive, saying in a study that Tehran last year boosted its capacity to build an atomic bomb.

The study, published by a body set by scientists from the top-secret Manhattan Project which built the world's first atomic bomb, comes as the United States and five other powers hold nuclear talks with Iran in Istanbul.

And it follows claims by US and Israeli officials that international efforts have slowed Iran's nuclear drive.

The Washington-based Federation of American Scientists said on its website that the gas centrifuges at Iran's main enrichment plant in Natanz became more efficient in 2010.

Centrifuges are the machines that enrich uranium for fuel in either civilian nuclear power plants or for a bomb's destructive power. Uranium must be enriched to 90 percent for a bomb, compared to five percent for power plants.

"Despite a drop in centrifuge numbers during 2010, the total enrichment capacity of Iran's main facility has increased relative to previous years," said the study authored by Ivanka Barzashka.