Iran said on Tuesday that, in its protracted talks with major powers to restore its tattered 2015 nuclear deal, it is insisting on resolving "four topics".

The four points, addressed by the government spokesman, relate to US assurances a new deal will hold, relief from punishing sanctions, and to the UN monitoring of Iranian sites.

"As Iran's president (Ebrahim Raisi) has said, we have pursued and will pursue four topics in the negotiations," the spokesman, Ali Bahadori-Jahromi, told a press briefing.

On the first point, he said that "the guarantees must be reassuring", referring mainly to Tehran's demand that future US administrations won't scrap the deal again, as Donald Trump's did in 2018.

"Objective and practical verification should be foreseen in the deal," he added, to ensure that sanctions are lifted not just on paper, and that international companies can return to Iran and operate freely.

Bahadori-Jahromi also said the "removal of sanctions should be meaningful and sustainable" as oil-rich Iran hopes to truly reap the economic benefits of sanctions relief.

And the spokesman stressed that "political claims about the safeguard issues should be closed", referring to Iran's claim a UN nuclear watchdog probe into unexplained nuclear particles found at various Iranian research sites is "political" and must end before a new deal is implemented.

The original nuclear deal promised Iran relief from crippling sanctions in return for guarantees it would not obtain a nuclear weapon, a goal Iran has always denied pursuing.

Trump withdrew the United States from the agreement in 2018 and reimposed heavy economic sanctions on Iran, prompting the Islamic republic to roll back on its commitments.

Iran has since April 2021 been engaged in EU-mediated talks to revive the deal, with Britain, China, France, Germany and Russia directly and the United States indirectly.

The European Union on August 8 put forward what it called a final text to restore the agreement, and Tehran and Washington then issued their responses and proposals.

Washington last Thursday labelled Tehran's latest response as "not constructive", adding that it would issue its own answer through the EU.

Bahadori-Jahromi said Tuesday that "negotiations about the agreement are continuing, but the other side should stop its excessive demands".