Iran and the UN nuclear watchdog held a new round of talks on Monday on Tehran's disputed atomic drive, the official IRNA news agency reported.
An unnamed source quoted by the agency said the talks, which meetings between Iranian officials and representatives of the International Atomic Energy Agency in April, would last three days.
The Iranian delegation is headed by Iran's ambassador to the UN agency, Ali Asghar Soltanieh while the agency's director for safeguard operations Herman Nackaerts is heading the IAEA team, the source said.
IAEA chief Mohamed ElBaradei is due to report in June on Iran's nuclear programme to the body's board of governors and the UN Security Council, which has imposed three sets of sanctions on Tehran over its nuclear defiance.
In April, Iran and the IAEA held two rounds of talks concentrating on allegations that the Islamic republic conducted studies on how to design a nuclear bomb.
The so called "weaponisation studies" stem from intelligence provided to the IAEA by some member states, but Iran insists that the talks are merely routine cooperation between the authorities and the agency.
Iran has refused to heed international demands to halt uranium enrichment, insisting that it has a right to the process to make nuclear fuel for meeting its increasing energy needs as a signatory to the nuclear Non-Proliferation Treaty.
Highly enriched uranium can also make the fissile core of an atom bomb, but Tehran has vehemently denied Western allegations it is seeking to acquire nuclear weapons.