Talks have begun in Vienna between Iranian negotiators and the United Nations nuclear watchdog agency.
Iran's delegation to Tuesday's meeting on Tehran's controversial nuclear program is headed by the country's deputy national security chief, Javad Vaeidi, and Ali Asghar Soltanieh, Iran's ambassador to the International Atomic Energy Commission.
The IAEA delegation is led by senior inspector Olli Heinonen.
Neither side made any comment as the talks began.
The U.N. Security Council has imposed two sets of sanctions on Iran because of its refusal to suspend uranium enrichment.
Enriched uranium and plutonium can be used to build nuclear weapons, but Iran says its nuclear program is for peaceful purposes.
The United States and its Western allies accuse Iran of trying to develop nuclear weapons.
Some information for this report was provided by AFP, AP and Reuters.