Iran's Bushehr plant may begin operations this year
Iran has enough nuclear material to build a bomb, the United States' most senior military commander has said.
"We think they do, quite frankly," Adm Mike Mullen, chairman of the US Joint Chiefs of Staff, told CNN.
"And Iran having a nuclear weapon, I've believed for a long time, is a very, very bad outcome for the region and for the world," he said.
Iran says its nuclear programme is entirely peaceful, but the West suspects it is seeking nuclear weapons.
'One bomb' possible
A report issued by the International Atomic Energy Agency (IAEA) two weeks ago said Tehran had built up a stockpile of fissile nuclear material.
This raised concerns in the West that Iran might have understated by one-third how much uranium it has enriched.
The IAEA report showed a major increase in Iran's reported stockpile of low-enriched uranium (LEU) since November to 1,010 kg.
Some physicists believe this stockpile is enough to be converted into enough highly enriched uranium to build one bomb.
The amount "is sufficient for a nuclear weapons breakout capability", David Albright, president of the Washington-based Institute for Science and International Security, told AFP news agency.
US Defence Secretary Robert Gates has adopted a more cautious approach.
"I think that there has been a continuing focus on how do you get the Iranians to walk away from a nuclear weapons programme? They're not close to a stockpile. They're not close to a weapon at this point," he told NBC on Sunday.
President Barack Obama has stated he wants to engage in diplomacy with Tehran to ensure it does not build nuclear weapons, and has described the country's nuclear programme as an "urgent problem" the international community must confront.