Diplomatic sources in Vienna say Iran has allowed United Nations inspectors to visit a nuclear reactor after denying them entry for the past year.
Speaking to media outlets on the condition of anonymity, diplomats said Thursday that Tehran allowed experts from the International Atomic Energy Agency to visit the Arak reactor last week.
IAEA officials have not commented on the information.
The Arak reactor is nearly completed and is intended to produce plutonium.
Iran says the overall purpose of its atomic program is to produce electricity. But the United States, other Western nations and Israel have accused Iran of working to develop a nuclear weapon.
Washington has given Iran until the opening of the U.N. General Assembly in September to take up an offer from six Western nations to discuss trade benefits if it freezes its uranium enrichment program. Enriched uranium could be used to make nuclear weapons.
U.S. officials say Iran could face harsher international sanctions if it refuses to hold talks.
Some information for this report was provided by AFP and AP.