The International Atomic Energy Agency's director-general plans to visit Iran on Sunday to try to defuse tension over what the nuclear watchdog says is Tehran's lack of cooperation.
Rafael Grossi will meet the Iranian vice president and the head of the Atomic Energy Organisation of Iran, Mohammad Eslami, the IAEA said in a statement on Saturday.
Grossi is expected to hold a press conference on his return to Vienna airport at around 8:30 pm (18:30 GMT), it added.
The visit comes after the agency issued a particularly harsh report earlier this week and ahead of a meeting of the IAEA board next week.
Since February 2021, verification and monitoring activities have been seriously hampered by Iran's restrictions on inspections, the document, seen by AFP, said.
President Ebrahim Raissi insisted that Iran was being "transparent".
Major powers, however, are losing patience, more than two months after the suspension of negotiations begun in April in Vienna under the aegis of the European Union to try to resurrect the international agreement of 2015.
The United States is close to abandoning its efforts, US Secretary of State Antony Blinken warned on Wednesday.
The Islamic Republic has been gradually freeing itself from its nuclear obligations since 2019, in response to Donald Trump's reinstatement of US sanctions.