Iran said nuclear talks that are set to resume Monday in Vienna should focus on lifting sanctions on the Islamic republic and "guarantees" the US will return to the fold.

Negotiations to salvage the 2015 Iran nuclear deal resumed in late November, after a five-month hiatus following the election of ultraconservative Iran President Ebrahim Raisi.

The talks seek to bring back the United States, after it withdrew from the accord in 2018 under president Donald Trump and began imposing sanctions on Iran.

Iran has reported progress in the talks, but European diplomats have warned they are "rapidly reaching the end of the road".

US negotiator Rob Malley has said there are only "weeks" left to revive the deal, if the Islamic republic continues its current pace of nuclear activities.

The talks are expected to get underway in the Austrian capital at 6:00 pm (1700 GMT), according to a source close to the negotiations.

Ahead of the resumption, Iran's Foreign Minister Hossein Amir-Abdollahian said the agenda on Monday should be "the issue of guarantees and verification" on the lifting of US sanctions if it returns to the accord.

"The most important thing for us is to reach a point where we can verify that Iranian oil will be sold easily and without any limits, that the money for this oil will be transferred in foreign currency to Iranian bank accounts, and that we will be able to benefit from all the revenues," he said, quoted on Monday by state news agency IRNA.

The opening of the eighth round of the talks involves delegations from Iran and the other countries that remain party to the landmark accord -- Britain, China, France, Germany and Russia.

The multilateral nuclear deal reached in 2015 offered Iran a lifting of economic sanctions in return for strict curbs on its nuclear activities.

The goal was to make it practically impossible for Iran to build an atomic bomb, while allowing it to pursue a civilian nuclear programme.

But the deal started to unravel in 2018 when the Trump administration pulled out and began imposing sanctions on the Islamic republic.

US President Joe Biden has said he is willing to return to the deal as long as Iran also resumes the original terms.

Positive message

Iran, which denies it wants to acquire a nuclear arsenal, has gradually abandoned its commitments to the accord since 2019, including by stepping up its enrichment of uranium.

The UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), recently expressed concerns over Iran's growing stockpile of highly-enriched uranium.

Iran's arch-rival Israel, which staunchly opposes the nuclear deal, had reportedly warned in November that the Islamic republic had taken the technical steps to prepare to enrich uranium to military-grade levels of around 90 percent.

On Saturday, Atomic Energy Organization of Iran director Mohammad Eslami said Tehran has no plans to enrich uranium beyond 60 percent, even if the Vienna talks fail.

Eslami said the enrichment levels were related to the needs of the country, in remarks published by the Russian news agency RIA Novosti.

"Our targets related to enriching uranium are meeting our industrial and production needs... and those of our people," he was quoted as saying.

Asked whether Iran plans to enrich beyond 60 percent purity if the talks fail, he said "No".

Moscow's ambassador to the UN in Vienna, Mikhail Ulyanov, welcomed that statement in a tweet on Sunday, calling it "a positive message on the eve of the 8th round" of the talks in Vienna.

"We advise all the participants in the negotiations to come to Vienna with the will to obtain a good agreement," Iran's foreign affairs spokesman Saeed Khatibzadeh said on Monday.