The International Atomic Energy Agency (IAEA) last week completed a long-awaited report that was expected to wrap up its investigation of Iran's nuclear programme. But the report has failed to make progress on the two major sticking points.

Iran is playing hardball.

According to sources close to the inquiry, the IAEA is keen to close the Iran file, but on two conditions. One is that Iran comes clean on any past weapons work. The other is that it agrees to the 'additional protocol' to the IAEA safeguards agreement, which gave extra powers to the IAEA in 1997, such as short-notice inspections of any site the agency wants to visit. This would give the IAEA greater confidence in being able to detect any clandestine facilities and operations.

Iran has not ratified the additional protocol, and although it voluntarily allowed broader inspection access from May 2004, it stopped doing so in January 2006. According to the report, released on 22 February, Iran has recently opened some sites to the IAEA, but the agency's director-general Mohamed ElBaradei says that this is “not, in my view, sufficient”. He adds that the additional protocol is “key for us to start being able to build progress in providing assurance that Iran's past and current programmes are exclusively for peaceful purposes”.

But Iran is playing hardball. It told the agency that it would comply with the additional protocol only “if the nuclear file [on Iran's nuclear capabilities] is returned from the security council to the IAEA”. Iran has also refused to comply with repeated calls by the United Nations Security Council — backed up with economic and political sanctions — to halt its uranium enrichment (see Nature 451, 750–751 ; 2008).

On the question of past suspect activities, the IAEA report says that it considers several to be “no longer outstanding”. These include work on polonium-210 and the Gchine uranium mine, which the military was suspected of being involved in running. The report adds, however, that for each issue cleared, it was still seeking “corroboration of its findings and to verify this issue as part of its verification of the completeness of Iran's declarations”.

But on the major item of allegations of direct nuclear weapons work, the report says that the IAEA “still awaits” adequate responses from Iran. These include details about the 'Green Salt' project, named after the common name of uranium tetrafluoride (UF4), a key intermediate in the production of uranium hexafluoride (UF6) for enrichment. It was part of an illicit project that the US Central Intelligence Agency says was described in a laptop computer it obtained in Iran, and that also described a possible clandestine processing plant and military connections, including tests related to nuclear weapons and missiles.

In a meeting with Iran from 3 to 5 February, the IAEA confronted it with new intelligence information relating to high-voltage detonators and an “explosive testing arrangement that involved the use of a 400-metre shaft and a firing capability remote from the shaft by a distance of 10 kilometres”. The report says that the IAEA believed both “would be relevant to nuclear weapon R&D”. Iran says the intelligence documents are fabricated.