Iran has moved to eliminate its most sensitive stockpile of enriched uranium gas under an interim nuclear deal with six world powers last year, according to a monthly UN nuclear watchdog update obtained by Reuters.
The report by the International Atomic Energy Agency showed that Iran had met the terms of the six-month agreement, which had been due to expire.
The agreement will now be extended with some adjustments, after Iran and the six powers failed to meet the 20 July deadline for a comprehensive agreement to end the decade-old nuclear stand off and agreed to continue talking.
The extension underlines the difficulties negotiators face in settling the dispute permanently even if Iran has met its commitments under the preliminary agreement, as the IAEA report suggests.
Under the 24 November accord, designed to buy time for talks on a long-term settlement of the dispute, Iran halted the most controversial aspect of its nuclear programme - enrichment of uranium gas to a fissile concentration of 20%.
It also undertook to dilute or convert to oxide its remaining stockpile of the material during the half-year period, which the IAEA report showed it had now completed.
That stockpile was closely watched by the West as the level of enrichment represented a relatively short technical step away from that required for nuclear weapons.
Iran says it is only refining uranium to fuel nuclear power plants or research reactors.
The IAEA update also showed that Iran had started-up a long-delayed facility to convert some of its lower-grade enriched uranium gas into oxide and had fed about 1,500kg of the material into the conversion process, as agreed under November's accord.