TIME reports that a spokesman for Admiral Mullen later clarified that he was referring to low-enriched uranium, which is not sufficient in itself to create a bomb. US intelligence agencies suspect Iran is creating the means to build a bomb under the cover of a nuclear energy program – a crucial distinction.
In its February report, the International Atomic Energy Agency said that Iran had roughly 1 metric ton of low-enriched uranium, which could be enough to arm a warhead, the Guardian reported last month. This assessment came as a surprise because the agency had said in November that Iran had produced only 635 kilograms of the fissile material. Iran has blocked inspectors from a nuclear reactor near the town of Arak and refuses to open up its centrifuge manufacturing facility.