Iran has continued to meet its commitments under an interim nuclear agreement with six world powers, a confidential United Nations nuclear agency report seen by Reuters showed on Monday.

The monthly update by the International Atomic Energy Agency said Iran was not enriching uranium above a fissile concentration of five per cent. It also said Iran had not made "any further advances" in its activities at two enrichment facilities and a heavy water reactor under construction.

Under the November 2013 accord between Iran and the United States, France, Germany, Russia, China and Britain, the Islamic Republic halted its most sensitive nuclear activity and took other steps in exchange for some easing of economic sanctions.

The pact was negotiated to buy time for talks on a final settlement of a dispute over the nature of a nuclear programme Iran says is peaceful but the West fears may be aimed at developing the capability to produce atomic bombs.

After reaching a framework agreement in marathon talks in Switzerland earlier this month, the parties are trying to nail down the details of a final settlement by the end of June. The next round of talks starts this week in Vienna.

US Under Secretary of State Wendy Sherman, Iranian Deputy Foreign Minister Abbas Araqchi and European Union political director Helga Schmid will conduct this session of talks.

Iranian Supreme Leader Ayatollah Ali Khamenei told military commanders on Sunday the United States had created the "myth" of nuclear weapons to portray Iran as a threat, hardening his rhetoric before the negotiations resume.