TEHRAN: Iran said Sunday it had held "fruitful discussions" with UN nuclear watchdog chief Rafael Grossi in Tehran, ahead of a deadline when it is set to restrict the agency's inspections unless the United States lifts painful sanctions.

Grossi's visit comes amid stepped-up efforts between US President Joe Biden's administration, European powers and Iran to salvage the 2015 nuclear deal that has been on the brink of collapse since Donald Trump withdrew from it.

Iran's Foreign Minister Mohammad Javad Zarif, before meeting Grossi, signalled that the Islamic republic wants to avoid an "impasse", but also warned it could step further away from its commitments if Washington does not lift the sanctions.

Grossi, head of the Vienna-based International Atomic Energy Agency (IAEA), arrived in Tehran late Saturday and met with the head of the Iran Atomic Energy Organisation, Ali Akbar Salehi.

"Iran and the IAEA held fruitful discussions based on mutual respect, the result of which will be released this evening," Tehran's ambassador to the UN agency Kazem Gharibabadi wrote on Twitter.

Grossi, who also met with Zarif later on Sunday, was due to hold a press conference when he returns to Vienna in the evening.

Iran's conservative-dominated parliament months ago demanded that, if the US does not lift sanctions by this Sunday, Iran suspend some IAEA inspections from Tuesday. But Iran has stressed it will not cease working with the IAEA or expel its inspectors.