VIENNA (REUTERS) - United Nations nuclear watchdog chief Rafael Grossi will fly to Teheran this weekend for talks that may ease a standoff between Iran and the West just as it risks escalating and scuppering negotiations on reviving the Iran nuclear deal.

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

Two said he would meet the new head of the Atomic Energy Organisation of Iran, Mr Mohammad Eslami, on Sunday (Sept 12).

The IAEA and Iran's envoy to the agency later confirmed the trip and the meeting. "Director-general Rafael Mariano Grossi will meet with Vice-President of the Islamic Republic of Iran and head of the AEOI, Mohammad Eslami, in Teheran on Sunday," the IAEA said, adding that Mr Grossi was expected to hold a news conference at Vienna airport around 8.30pm on Sunday.

The IAEA informed 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 the agency can continue to keep track of parts of Iran's nuclear programme as provided for by the 2015 deal.

Separate, indirect talks between the United States and Iran on both returning to compliance with the 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.

Under the 2015 deal between Iran and major powers, Teheran agreed to restrictions on its nuclear activities in exchange for the lifting of sanctions.

President Donald Trump pulled the United States out of the deal in 2018, re-introducing painful economic sanctions.

Iran responded as of 2019 by breaching many of the deal's core restrictions, like enriching uranium to a higher purity, closer to that suitable for use in nuclear weapons.

Western powers must decide whether to push for a resolution criticising Iran and raising pressure on it for stonewalling the IAEA at next week's meeting of the agency's board of governors.

A resolution could jeopardise the resumption of talks on the deal as Teheran bristles at such moves.