IT is one of the most memorable phrases of George W Bush's presidency so far. In his 2002 State of the Union address, the first after the September 11 attacks, the president spoke of the "axis of evil", made up of Iraq, Iran and North Korea, whose determination to secure nuclear weapons posed as great a threat to the US as terrorism.

Just over 12 months later, the US invaded Iraq, ostensibly to eliminate the danger from one of the members of this group. The justification was Saddam Hussein's refusal to abandon attempts to develop weapons of mass destruction, chemical and biological as well as nuclear weapons. Now, there are fears that the second member of this axis could be in the crosshairs.

Although there had long been suspicions that Iran was attempting to develop its own nuclear capability, confirmation came only in September 2002, when exiled opponents of the Tehran regime claimed that plants had been built at two sites as part of an atomic programme. It was subsequently revealed that Iran had been working on the programme in secret for 18 years.

Iran insists that its ambitions are purely civilian. That, despite its huge oil and gas reserves, it wants a diverse supply of energy, and that it has a right to develop nuclear power, but has no interest in making nuclear weapons.

But the US is suspicious, fuelled by that 18-year secrecy. In order to develop a nuclear bomb, Iran would need its own nuclear programme, and the discovery of highly enriched weapons grade uranium by the UN's nuclear watchdog, the International Atomic Energy Authority (IAEA), and reports that the man behind Pakistan's nuclear bomb, Abdul Qadeer Khan, had sold weapons technology to Iran, has exacerbated those fears.

What has brought this crisis to a head is the failure of negotiations between Iran and the EU Three, Britain, France and Germany. The EU came up with a proposal to allow Iran to develop its nuclear programme if it halted its uranium enrichment work. The raw uranium, known as yellowcake, needs to be enriched for use in nuclear power plants, and enriched still further for use in a bomb. The EU proposal, backed by the US, would see Iran supplied with enriched uranium by other countries, but without the capacity to carry out the process, and therefore to enrich it further for weapons use, itself.

Tehran rejected this compromise at the weekend, claiming that these suppliers could come under US influence and could not be trusted, and instead announced it would restart work on its nuclear plant at Isfahan, suspended since the negotiations began last November. Iranian scientists are also working on a heavy water reactor, which could provide plutonium, an alternative to enriched uranium for use in nuclear weapons.

The result was yesterday's emergency meeting of the IAEA, and an expected referral to the UN Security Council. Although the US has said it favours a diplomatic solution, it has publicly stated that it will not permit Iran to develop nuclear weapons. There have also been reports that Israel, which bombed an Iraqi reactor in 1981 and is fearful of nuclear weapons in the hands of its enemies, has begun planning for a possible raid on Iran.

On top of this, Iran's new hardline president, Mahmoud Ahmedinejad, took office last week, and one of his first actions was to replace his chief nuclear negotiator with a conservative former head of state broadcasting, who is known to have close ties with the Supreme Leader, Ayatollah Ali Khamenei.

But while international tension escalates, prompting fears that at the very least it could lead to a worsening of relations between the West and the Muslim world, and at the worst that it could end in military confrontation, Dr Mahoob Zweiri, director of the Centre for Iranian Studies at Durham University, believes it could result in the previously unthinkable: a diplomatic rapprochement between the US and Iran.

"I believe it is the first step to seeing Americans and Iran around the table together," he says. The alternatives are sanctions or war, but Iran has been subject to US sanctions since the Shah was toppled in 1979 and has still been able to develop its nuclear programme. Sanctions could also be vetoed by Russia and China, which both have economic interests in Iran and are opposed to the strengthening of US power. And although the rapid victory in Iraq may have given the US confidence, the subsequent turmoil seems to have sapped any enthusiasm for another military adventure.

"There is no solidarity in the international community against Iran, and Iran understands that very well," says Dr Zweiri. He says the failure of the negotiations with the EU 3 highlights the fact that it is the US that is the real active player in international relations, and it is with the US that Iran needs to speak.

"There are a lot of issues that Iran wants to discuss with the United States direct: what happened to Iranian money after the revolution, economic sanctions, the role of Iran in central Asia, Iraq, Hezbollah, the Shia Muslims in the Persian Gulf, and this is the first step towards negotiation," he says.

"And the situation in Iraq shows that the United States is not keen to take any military action against Iran." Instead, he says, the US is keen to withdraw from both Iraq and central Asia, which would only be made possible if the region became more stable. A war would also send the price of oil, already disastrously high, soaring still further, threatening to cripple the global economy, he adds.

There have also been two key developments which have indicated the willingness of the US to negotiate. The first was the acceptance, for the first time, of Iran's right to develop a civilian nuclear programme. The second was a report in the Washington Post that it would take Iran ten years to develop a nuclear bomb.

"That was a clear message that the Americans know how far they are from building a nuclear bomb, particularly as it came a couple of days before the new president took office in Iran," he says.

But if both sides have much to gain from direct negotiations, there are still substantial obstacles. The US needs to persuade Israel that Iran does not represent a threat to their security, and the Iranian leaders need to convince their own people of the benefits from talking to the Americans.

"Really, this is not a nuclear issue, it is a political issue," says Dr Zweiri. "By sitting down together they can look at the crisis between Iran and the United States, and I think this is the first step to that."