Iran obtained detailed instructions on how to set up the complicated process of enriching uranium, which can be used to make nuclear arms, from the black market network of Pakistani scientist Abdul Qadeer Khan, the UN atomic monitoring agency said on Friday.
In a report, the International Atomic Energy Agency praised Iran for increased cooperation with IAEA experts probing its nuclear programme for signs it might have been used to develop weapons.
But it also said more transparency was "indispensable and overdue" on the part of Tehran, as agency inspectors try to determine if the military secretly ran its own nuclear program parallel to a civilian one.
For that, said the document IAEA inspectors had to have access both to more details on Iran's enrichment activities and a site where it is believed to be storing equipment that could be used in a weapons programme.