Iran has met a key demand of the United Nations nuclear agency it emerged last night, by handing over long-sought after blueprints showing how to mold uranium metal into the shape of warheads.
Iran's decision to release the documents, which were seen by UN inspectors two years ago, was seen as a concession designed to head off the threat of new UN sanctions.
However, diplomats said Tehran has failed to meet other requests made by the International Atomic Energy Agency in its attempts to end nearly two decades of nuclear secrecy on the part of Iran.
IAEA chief Mohamed ElBaradei is currently completing his latest report to his agency's 35-nation board of governors for consideration next week.
While Mr ElBaradei is expected to say that Iran has improved its cooperation with his agency's probe, the findings are unlikely to deter the United States, France and Britain from pushing for a third set of UN sanctions.
The agency has been seeking possession of the blueprints since 2005, when it stumbled upon them among a batch of other documents during its examination of suspect Iranian nuclear activities.
While agency inspectors had been allowed to examine them in the country, Tehran had up to now refused to let the IAEA have a copy for closer perusal.
Diplomats accredited to the agency said the drawings were hand-carried by Mohammad Saeedi, deputy director of Iran's Atomic Energy Organisation and handed over last week in Vienna to Oli Heinonen, an ElBaradei deputy in charge of the Iran investigations.
Both the IAEA and other experts have categorised the instructions outlined in the blueprints as having no value outside of a nuclear weapons program.
While ElBaradei's report is likely to mention the Iranian concession on the drawings and other progress made in clearing up ambiguities in Iran's nuclear activities, it was unclear whether it would also detail examples of what the diplomats said were continued Iranian stonewalling.
Senior IAEA officials were refused interviews with at least two top Iranian nuclear officials suspected of possible involvement in a weapons program, they said. One was the leader of a physics laboratory at Lavizan, outside Tehran, which was razed before the agency had a chance to investigate activities there. The other was in charge of developing Iran's centrifuges, used to enrich uranium.
AP