TEHERAN (AFP, REUTERS) - Iran will "automatically" return to its nuclear commitments if United States President-elect Joe Biden lifts sanctions imposed over the past two years, its foreign minister said on Wednesday (Nov 18).

Teheran's return to its commitments "can be done automatically and needs no conditions or even negotiations", Mr Mohammad Javad Zarif said in comments published in the state-run Iran daily.

Decades-old US-Iranian tensions escalated after US President Donald Trump unilaterally withdrew from a landmark nuclear agreement in 2018 and reimposed, then reinforced, crippling sanctions.

While Mr Trump has sought to maximise pressure on Iran and isolate it globally, Mr Biden has proposed to offer the Islamic republic a "credible path back to diplomacy".

Mr Zarif argued that "America is obligated to implement Resolution 2231 as a member of the United Nations and its Security Council", pointing to the UNSC resolution that enshrined the 2015 nuclear deal.

"If it does carry out this resolution and sanctions are lifted and there are no obstacles to Iran's economic activities, then Iran will carry out" its obligations under the deal, he said.

Iran, which denies it is seeking to build a nuclear bomb, has since May 2019 gradually suspended most of its key obligations under the agreement.

It argued it was reacting to the sanctions and the inability of the other parties - Britain, China, France, Germany and Russia - to provide Teheran with the deal's promised economic benefits.

Mr Zarif described Mr Biden as a "foreign affairs veteran" whom he has known for 30 years.

Once in the White House, Mr Biden could "lift all of these (sanctions) with three executive orders", Mr Zarif argued.

If Mr Biden's administration does so, Iran's return to nuclear commitments will be "quick", the minister added.

Washington's return to the deal, however, could wait, Mr Zarif added.

"The next stage that will need negotiating is America's return... which is not a priority," he said.

"The first priority is America ending its law breaking and rebelling."

The New York Times reported on Monday that Mr Trump had last week asked top aides about the possibility of striking Iran's nuclear facilities at Natanz.

Senior officials reportedly "dissuaded the president from moving ahead with a military strike", warning him that such an attack could escalate into a broader conflict in the last weeks of his presidency.

A report by the UN atomic watchdog obtained by Reuters on Wednesday showed Iran has fired up advanced uranium-enriching centrifuges that it had installed underground at its Natanz site, in the latest breach of its nuclear deal with major powers.

The deal states that Iran can only accumulate enriched uranium with first-generation IR-1 machines and that those are the only centrifuges it can operate at its underground plant at Natanz, apparently built to withstand aerial bombardment.

An International Atomic Energy Agency (IAEA) report last week showed Teheran had installed a cascade, an interlinked cluster, of advanced IR-2m machines underground at Natanz, having moved them from an above-ground plant where it was already enriching uranium with advanced centrifuges in breach of the deal.

Last week's report said it had not fed uranium hexafluoride (UF6) gas, the feedstock for centrifuges, into that cascade.

"On 14 November 2020, the Agency verified that Iran began feeding UF6 into the recently installed cascade of 174 IR-2m centrifuges at the Fuel Enrichment Plant (FEP) in Natanz," the IAEA report to member states dated Tuesday said.

Iran has breached many restrictions imposed by the 2015 deal on its atomic activities, including on the purity to which it enriches uranium and its stock of enriched uranium. These breaches came in response to Mr Trump's withdrawal from the nuclear deal in 2018 and the reimposition of US sanctions against Teheran that had been lifted under the accord.

Last week's IAEA report said Iran had also begun installing a cascade of IR-4 centrifuges at the underground plant but not a planned third cascade of IR-6 machines. It is also operating 5,060 IR-1 machines at the underground plant.