The U.N. nuclear watchdog's 35-nation board of governors on Friday backed the reappointment of Argentina's Rafael Grossi to a second four-year term as director general, diplomats at the closed-door meeting said.

The decision was a formality since there was no challenger.

The International Atomic Energy Agency's board approved his reappointment by acclamation, meaning that no vote was held and no country expressed opposition, diplomats said. The decision is subject to approval by the IAEA's General Conference, an annual meeting of all member states held in the autumn.

The General Conference is expected to approve it. Grossi's current term ends in December.

Grossi has overseen a turbulent period in relations with Iran, since the Islamic Republic started breaching restrictions imposed on its nuclear activities by the 2015 Iran nuclear deal with major powers the year he took office.

Iran's steps, which have now gone well beyond those curbs, followed the United States' withdrawal from the deal in 2018 under then-President Donald Trump, which re-imposed U.S. sanctions against Iran.

The IAEA is policing that deal although it is not a party to it, and it is also locked in a years-long standoff with Iran over the separate issue of uranium particles found at three undeclared sites, which Iran has yet to explain credibly.

After Grossi visited Iran this weekend, both sides issued a joint statement

saying Iran was prepared to hand over more information on the traces and allow more monitoring related to the 2015 nuclear deal, but the statement went into few details and is subject to further talks.

Grossi, a more vocal IAEA chief than his Japanese predecessor Yukiya Amano, who died in office, has also been trying to broker a protection zone around the Russian-held Zaporizhzhia nuclear power plant in Ukraine,

Shelling near Zaporizhzhia, which Russia and Ukraine have blamed on each other, has repeatedly cut external power lines needed to cool reactor fuel and avoid a potentially catastrophic meltdown at Europe's biggest nuclear power plant. (Reporting by Francois Murphy; Editing by Alex Richardson and Nick Macfie)