Iran has enough low-enriched uranium to make two weapons, which it could have prepared and ready for delivery as early as 2012, CIA director Leon Panetta warned on Sunday.
"We think they have enough low-enriched uranium for two weapons," Panetta told the ABC network's "This Week" programme.
Tehran would need a year to enrich it fully to produce a bomb and it would take "another year to develop the kind of weapon delivery system in order to make that viable," he said.
Iran is under mounting international pressure over its suspect nuclear programme, which the West fears masks a covert weapons drive.
The US Congress this week endorsed a sweeping package of tough new energy and financial sanctions on Tehran over the program. The Islamic republic vehemently denies the charge, but has been flexing its military muscle mainly in the strategic Gulf region by staging regular war games and showcasing an array of Iran-manufactured missiles.
Neither the United States nor its top regional ally Israel, the sole if undeclared nuclear-armed power in the Middle East, have ruled out a military strike to curb Iran's atomic drive.
On June 10, the UN Security Council adopted resolution 1929, which imposed military and financial sanctions on Iran aiming to rein in the suspect nuclear drive.