Rafael Grossi met the chief of the Atomic Energy Organization of Iran, Mohammad Eslami, who is also one of Iran's vice presidents.

Grossi's visit comes as talks remain locked in Vienna on saving Tehran's 2015 deal with major powers that promised it sanctions relief in return for curbs on its nuclear programme.

The landmark deal was torpedoed in 2018 by then US president Donald Trump's unilateral decision to withdraw Washington from it and impose a punishing sanctions regime.

Iran has since stepped away from many of its commitments, but the administration of US President Joe Biden has advocated a return to diplomacy to save the agreement.

A point of contention this year has been limits Iran has imposed on the IAEA's ability to monitor various of its nuclear facilities.

Iran has refused to provide real-time footage from cameras and other surveillance tools that the UN agency has installed in these locations.

Under a compromise deal, the monitoring equipment remains in the agency's custody but the data is in Iran's possession, and must not be erased as long as the arrangement remains in force.

Initially agreed for three months, the compromise was extended by another month and then expired on June 24. The IAEA has since been urging Tehran to inform it of its intentions.

The state-run Iran newspaper said Sunday the two sides would discuss "the temporary arrangement... on the supervision of IAEA inspectors and the contents of IAEA surveillance cameras installed in Iranian nuclear centres".

- Stalled talks -

The issue has heightened tensions at a time the new government of Iran's ultraconservative President Ebrahim Raisi has taken charge in Tehran.

The IAEA said in a statement last Tuesday that its "verification and monitoring activities have been seriously undermined" by Tehran's actions.

It also said that Iran had boosted its stocks of uranium enriched above the levels allowed in the 2015 deal formally known as the Joint Comprehensive Plan of Action.

Raisi argued in a statement on Wednesday that his country was "transparent" about its nuclear activities, which Iran has always insisted are peaceful.

"Naturally, in the event of a non-constructive approach by the IAEA, it is unreasonable to expect Iran to respond constructively," he said.

Grossi -- who is on his second trip to Iran this year -- was expected to hold a press conference on his return to Vienna airport around 8:30 pm (1830 GMT).

A meeting of the agency's board of governors is scheduled for Monday.

US Secretary of State Antony Blinken cautioned last Wednesday that, faced with the impasse, the United States is "close" to abandoning its diplomatic efforts.

Israeli Prime Minister Naftali Bennett on Friday charged that the IAEA report "proves that Iran is continuing to lie to the world and advance a programme to develop nuclear weapons, while denying its international commitments".