For the first time, an International Atomic Energy Agency report suggested Iran was actively pursuing nuclear weapons capability, throwing independent weight behind similar Western suspicions.
The IAEA seemed to be cautiously going public with concerns arising from a classified agency analysis leaked in part last year which concluded that Iran has already honed explosives expertise relevant to a workable nuclear weapon.
The report also confirmed Iran had produced its first small batch of uranium enriched to a higher purity and had set aside the vast bulk of its low-enriched uranium stockpile for this purpose even though this seemed far in excess of possible civilian needs.
For several years, the IAEA has been investigating Western intelligence reports indicating Iran has coordinated efforts to process uranium, test explosives at high altitude and revamp a ballistic missile cone in a way suitable for a nuclear warhead.
'The information available to the agency is extensive, broadly consistent and credible in terms of the technical detail, the time frame in which the activities were conducted and the people and organizations involved,' the report said.
'Altogether this raises concerns about the possible existence in Iran of past or current undisclosed activities related to the development of a nuclear payload for a missile.'
IAEA's new chief, Yukiya Amano, is seen as more inclined to confront Iran than his predecessor, Mohamed ElBaradei, who retired on December 1.
'Now we see from (available intelligence) that certain activities may have continued after 2004,' said a senior official close to the IAEA. 'We want to find out from Iran what they've had to do with these nuclear explosive-related activities.'
Iran has dismissed the intelligence reports as fabrication but failed to provide its own evidence. Tehran has boycotted contact with the IAEA on the matter for 18 months.
The report, to be considered at a March 1-5 meeting of the IAEA's 35-nation board, said it was vital for Iran to cooperate with IAEA investigators 'without further delay.'