US alert as Iran boosts uranium enrichment

The US said today that revelations that Iran is enriching uranium to higher levels show a "further escalation" of its flouting of UN rules.

Washington again called on Tehran to halt its nuclear programme after the International Atomic Energy Agency confirmed it had intelligence suggesting uranium was being enriched to 20 per cent at an underground site.

Experts claim enriching to 20 per cent is an important step towards producing material suitable for use in nuclear weapons. The UN nuclear watchdog added that the atomic material at the site, in Fordow, near the Shia Muslim holy city of Qom, remained under its surveillance.

State Department spokeswoman Victoria Nuland said: "The fact that the IAEA has made clear that they are enriching to a level that is inappropriate at Fordow is obviously a problem.

"If they are enriching at Fordow to 20 per cent, this is a further escalation of their ongoing violations with regard to their nuclear obligations."

The bunker in Fordow is built into a mountainside and heavily fortified, making it a difficult target for an air strike. The US and Israel refuse to rule out using force if Iran continues to ignore nuclear restrictions.

The UN's warning comes a day after an American was sentenced to death in Iran for allegedly passing secrets back to Washington. Arizona-born Amir Mirzaei Hekmati was accused of being a CIA agent during his trial - a charge he and his family deny.