UN nuclear watchdog chief Rafael Grossi will fly to Tehran this weekend for talks that may ease a standoff between Iran and the West just as it risks escalating negotiations on reviving the Iran nuclear deal, diplomats said on Saturday.

Three diplomats who follow the International Atomic Energy Agency (IAEA) closely said Grossi's trip before next week's meeting of the IAEA's 35-nation board of governors was confirmed.

One told Reuters that Grossi would arrive in Tehran early on Sunday and meet the head of the Atomic Energy Organization of Iran.

The IAEA informed its member states this week that there had been no progress on two central issues: explaining uranium traces found at several old, undeclared sites and getting urgent access to some monitoring equipment so that the agency can continue to keep track of parts of Iran's nuclear program as provided for by the 2015 deal.

Separate, indirect talks between the United States and Iran on both returning to compliance with the nuclear deal have been halted since June. Washington and its European allies have been urging hardline President Ebrahim Raisi's administration, which took office in August, to return to the talks.