Iranians 'ready to detonate nuclear bomb in a year'

If and when Supreme Leader Ayatollah Ali Khamenei gives the order, it is feared that uranium enrichment and the assembly of the warhead could happen in the next 12 months.

The sources added it is not yet known if he has already made the decision to build.

It is further believed the Iranian Defence Ministry has been operating a secret nuclear scheme for years, alongside Tehran's civilian nuclear programme. The US has set a deadline of until next month for Iran to come in from the cold over its nuclear ambitions or face harsh sanctions.

Israel is still talking in terms of military strikes, and alleges that Iran has already got enough enriched plutonium to build one nuclear warhead. Amid concerns over the perceived nuclear threats from North Korea as well as Iran, the Pentagon is seeking to speed deployment of an ultra-large "bunker-buster" bomb on the most advanced US bombers by next July.

The Air Force said on Sunday that the non-nuclear, 30,000lb Massive Ordnance Penetrator, which is still being tested, is designed to destroy deeply-buried bunkers beyond the reach of existing bombs.

The device can penetrate up to 200ft underground before exploding.

The suspected nuclear facilities of Iran and North Korea are believed to be largely buried underground to escape detection and boost their chances of surviving attack.

Kenneth Katzman, an Iran expert at the Congressional Research Service, the research arm of the US Congress, said: "It's very possible that the Pentagon wants to send a signal to various countries, particularly Iran and North Korea, that the US is developing a military option against their nuclear programmes."

Ayatollah Khamenei yesterday endorsed the presidency of Mahmoud Ahmadinejad in a ceremony boycotted by leading moderates in protest at the results of disputed elections that plunged Iran into its worst crisis since the 1979 Islamic Revolution.

Two former presidents, Akbar Hashemi Rafsanjani and Mohammad Khatami, who backed defeated candidate Mirhossein Mousavi, did not attend yesterday's ceremony although they had been present at such events in the past.

"I am endorsing the presidency of this brave, hard-working and wise man as the president of the Islamic Republic of Iran," Ayatollah Khamenei said, in praise of Mr Ahmadinejad who is due to be sworn in by parliament tomorrow.

After the ceremony, hundreds of Mr Mousavi's supporters, some of them honking car horns, headed towards a central Tehran square where they planned to protest.

Dozens of riot police and Basij militia had assembled to prevent any demonstration taking place but were not intervening, a witness said.

Other leading moderate figures joined Mr Rafsanjani, who has declared the country in crisis, and Mr Khatami in missing the formal endorsement.