A new report by the Foreign Policy Center warned that the 'gravest threat' was not posed by so-called 'rogue states' but from countries with weak controls 'in which nuclear weapons and materials are readily available'.

Apart from Pakistan and Russia, it listed Ukraine, Ghana and Nigeria as a much greater risk from their weapons and nuclear enrichment programs.

The author of the report, Amitai Etzioni, is credited with being a prime intellectual influence on the development of Blair's Third Way politics. He also acted as a senior advisor to former US president Bill Clinton.

In his criticism of western policies, he argued that US President George W Bush's emphasis on his discredited 'Axis of Evil' was misplaced. "Nuclear attacks in this day and age are much more likely to be the work of terrorists," he warned.

It was the endemic corruption and ineffective controls in Moscow that made Russia the 'failing state of greatest concern', his report said.

It also said the US should stop transporting highly-enriched uranium from other eastern European states, such as Serbia, Romania and Bulgaria, for dismantling.

With regard to Iran, Etzioni said that it was a blunder to call for 'an Iraqi-style regime change'. Occupying this large country, whose citizens 'are fiercely patriotic would be a costly mistake', he warned.

"The notion that one can find a viable opposition group that would use American arms against their own government is at best a long shot," he said in his report.

"Nor can one expect the support of the international community given that whatever will there was for such pre-emptive action was largely squandered on the invasion of Iraq," it said.

But the report also argued that Iran should be treated differently to North Korea, after its admission it has a nuclear weapons capability.

It suggested that while North Korea should be admitted to the 'nuclear club', it emphasized that it should be the 'last member' while Iran 'can still be defanged'.

Etzioni controversially called for Iran's nuclear facilities to be attacked with bombs. "People who live there should be given warning to leave the areas before they are attacked," he said, adding that 'special bombs' would be needed to neutralize the sites.