TEHRAN: International Atomic Energy Agency (IAEA) chief Rafael Grossi met Iran's top diplomat Thursday as he began crunch nuclear talks in Tehran weeks before US President-elect Donald Trump takes office.

During his first term in the White House from 2017 to 2021, Trump was the architect of a policy called "maximum pressure" which reimposed sweeping US economic sanctions that had been lifted under a landmark 2015 nuclear deal.

Grossi, who arrived in Tehran late Wednesday, is expected "to negotiate with the country's top nuclear and political officials," IRNA state news agency reported.

Grossi described the meeting with Foreign Minister Abbas Araghchi as "indispensable" in a post on X. Araghchi was Iran's chief negotiator in the talks that led to the 2015 deal.

Grossi also met the head of Iran's Atomic Energy Organisation, Mohammad Eslami, the Tasnim news agency reported.

Later, the IAEA chief is expected to meet President Masoud Pezeshkian for their first talks since his election earlier this year.

Grossi's visit is his second to Tehran this year but his first since Trump's re-election.

In 2018, Trump unilaterally abandoned the 2015 deal that gave Iran relief from international sanctions in exchange for restrictions on its nuclear programme designed to prevent it developing a weapons capability, an ambition it has always denied.

The following year, Iran started to gradually roll back its commitments under the deal, which barred it from enriching uranium to above 3.65 per cent.

The IAEA says Iran has significantly expanded its stocks of uranium enriched to 60 per cent, a level that has triggered international alarm as it is much closer to the 90 per cent level needed for a nuclear warhead.

Grossi "will do what he can to prevent the situation going from bad to worse" given the significant differences between Tehran and Western capitals, said Ali Vaez, an Iran specialist at the Crisis Group, a US-based think tank.

Iran has blamed the incoming US president for the standoff.

"The one who left the agreement was not Iran, it was America," government spokeswoman Fatemeh Mohajerani said on Wednesday.

"Mr. Trump once tried the path of maximum pressure and saw that this path did not work."

Grossi's visit comes just days after Israeli Defence Minister Israel Katz said Iran was "more exposed than ever to strikes on its nuclear facilities".

The arch foes have exchanged unprecedented direct attacks in recent months as tensions have soared during the intensifying war between Israel and Iran allies Hamas in Gaza and Hizbollah in Lebanon.

Trump's looming return to the White House in January has only added to international fears of all-out conflict between Israel and Iran.

"The margins for manoeuvre are beginning to shrink," Grossi warned in an interview with AFP on Tuesday, adding that "it is imperative to find ways to reach diplomatic solutions".

Grossi has said that while Iran does not currently have a nuclear weapon, it does have plenty of enriched uranium that could eventually be used to make one.

Iran's new president, who won election in July on a platform to improve ties with the West, has said he wants to revive the 2015 deal.

 - AFP