Two rounds of talks between Iran, the five permanent members of the U.N. Security Council and Germany concluded in Kazakhstan early this year with few breakthroughs.
Inspectors from the International Atomic Energy Agency this year said they haven't been able to verify whether Iran's nuclear program is entirely for peaceful purposes.
A source close to the Iranian negotiating team told Iran's state-funded broadcaster Press TV on condition of anonymity there were no agreements yet on future talks with the IAEA.
Iranian officials this week said there are no plans to enrich uranium to 20 percent purity, considered a benchmark in the development of a nuclear weapon. Enrichment could take place up to 50 percent purity for special uses, such as to fuel Iran's nuclear submarine fleet, however.
Iranian Supreme Leader Ali Khamenei suggested it was against his country's principles to pursue nuclear weapons. Iran maintains it has the right to a peaceful nuclear program as a party to the Nuclear Non-proliferation Treaty.