International Atomic Energy Agency (IAEA) director general Rafael Grossi "requests Iran to work with the agency in earnest and in a sustained way towards the fulfilment of the commitments," the agency said in a confidential report seen by AFP.

Tehran in March vowed to reactivate surveillance devices which were disconnected in June 2022 amid deteriorating relations with the West.

In a separate report, also seen by AFP, the IAEA said Iran's total stockpile of enriched uranium was lower than in May but still more than 18 times the limit set in a 2015 accord between Tehran and world powers.

Iran's total enriched uranium stockpile was estimated at 3,795.5 kilogrammes (8,367.7 pounds) as of August 19, down by 949 kilogrammes from May, the agency said.

The limit in the 2015 deal was set at 202.8 kilogrammes.

The stockpile of uranium enriched up to 60 percent is now at 121.6 kilos, up from 114.1 kilos in May.

Iran also has 535.8 kilos of uranium enriched up to 20 percent, up from 470.9 kilos in the last May report.

The landmark 2015 deal -- curbing Iran's nuclear programme in exchange for sanctions relief -- started to fall apart in 2018 when the US unilaterally withdrew from it and reimposed sanctions.

Efforts to revive it -- bringing Washington back into the deal and scaling back Tehran's programme again -- have been fruitless so far with European-led talks on hold since 2022.

Tensions between Tehran and Washington eased last month with the announcement of an agreement for Iran to release five American prisoners in exchange for the return of $6 billion in Iranian funds frozen in South Korea.

But the delicate agreement does not include the possibility of a return to the nuclear deal in the run-up to the 2024 US presidential election.