The document is intended to maintain pressure on Iran to fully declare aspects of its previously covert nuclear program.

IAEA chief Mohamad el-Baradei reflected the organisation's frustration with Iran and said the investigation 'can't go on forever'.

'These are two issues where we need accelerated and proactive cooperation,' El-Baradei said. 'The way they have been engaging us on these issues has been less than satisfactory.'

A resolution calling for increased cooperation and disclosure is likely to be presented later in the week.

In Washington, State Department spokesman Richard Boucher said El-Baradei's remarks were further evidence of Tehran's lack of co-operation. He said the US wants IAEA's board to back a strong resolution calling for Tehran's full co-operation to resolve all outstanding nuclear issues. The US stopped short of recommending Iran's referral to the UN Security Council, saying that the IAEA's investigations were 'valuable'.

Iranian President Mohammad Khatami reacted to the IAEA resolution on 15 June by warning Britain, France and Germany to stop pressuring Tehran over its nuclear programme or risk pushing Iran to consider 'other alternatives' to co-operating with UN inspections. In the Tehran Times newspaper, Khatami wrote that 'Iran will not forego its inalienable right to nuclear energy for peaceful purposes', and that 'if such confrontational behaviour continues, Iran will contemplate other alternatives'.