US President Barack Obama, Britain's Prime Minister Gordon Brown and French President Nicolas Sarkozy have joined forces to accuse Iran of concealing a covert nuclear plant, and to warn Iran of sanctions unless the issue is resolved.
The public accusation and warning comes just hours after Tehran revealed the existence of a second uranium enrichment plant, which it insisted was intended for civil energy-generating purposes.
Iranian officials said details of the plant were disclosed to the head of the International Atomic Energy Agency, Mohamed ElBaradei, in a letter on Monday.
There was speculation that the announcement was designed to pre-empt the joint statement by the US, British and French leaders at the G20 summit in Pittsburgh, Pennsylvania, today.
The statement is expected to increase pressure on Tehran ahead of international talks in Istanbul on October 1 at which the E3+3 group of Britain, France, Germany, the US, Russia and China will confront Iran over its disputed nuclear programme.
Iran, which is subject to United Nations Security Council sanctions because it refuses to halt uranium enrichment, has previously admitted to only one facility.
It says that its activities are intended for peaceful electricity generation, but the same enrichment processes can produce both nuclear fuel and material for warheads.
Mr Brown warned Iran yesterday that it faced "far tougher" sanctions unless it was prepared to give up its controversial nuclear programme, and he repeated that warning today.
Speaking earlier in New York ahead of a special meeting of the UN Security Council on nuclear non-proliferation, chaired by Mr Obama, the Prime Minister said the issue was “coming to a head”.
Iran is under three sets of UN Security Council sanctions for refusing to halt enrichment at what had been its single known enrichment plant, which is being monitored by the IAEA.
It claimed that the 'new' plant - which President Obama said was actually in existence for some years - would not enrich uranium beyond the 5% level suitable for civilian energy production. That would be substantially below the threshold of 90% or more needed for a weapon.
Sources said that Iran’s letter contained no details about the location of the second facility, when – or if – it had started operations or the type and number of centrifuges it was running.
But one source said it was about 100 miles south-west of Tehran and was the site of 3,000 centrifuges that could be operational by next year.
Iran had previously claimed to have only one plant and had denied allegations of undeclared nuclear activities.
An August IAEA report said Iran had set up more than 8,000 centrifuges to churn out enriched uranium at its cavernous underground facility outside the southern city of Natanz. The report said that only about 4,600 centrifuges were fully active.
Iran says it has the right to enrich uranium for a nationwide chain of nuclear reactors. But because enrichment can also produce weapons-grade uranium, the international community fears Tehran will make fissile material for nuclear warheads.
The revelation hinders the chances of progress in scheduled talks between Iran and six world powers on October 1.
At that meeting – the first in more than a year – the five permanent UN Security Council members and Germany plan to press Iran to scale back on its enrichment activities. But Tehran has declared that it will not bargain on enrichment.
Mark Fitzpatrick, senior fellow for non-proliferation at the International Institute for Strategic Studies, suggested that Iran had little choice about disclosing the secret site ahead of the G20 meeting in Pittsburgh.
“Iran undoubtedly announced it to the to the IAEA because they were afraid it would become known to the US and others,” he said.
Mr Fitzpatrick said the disclosure “will add to the momentum behind a push for stronger sanctions on Iran” should the Oct. 1 talks in Geneva fail.
The existence of a secret Iranian enrichment programme built on black-market technology was revealed seven years ago. Since then, the country has continued to expand the program with only a few interruptions as it works toward its aspirations of a 50,000-centrifuge enrichment facility at Natanz.