"We are thinking about how to reach a strong text on the issue of the guarantee, and to obtain stronger guarantees," he told a joint news conference in Moscow with his Russian counterpart Sergei Lavrov.

"My colleagues are carefully examining the text of the American side," Amir-Abdollahian said of Washington's response to Tehran's suggestions on the EU text that was submitted on August 8.

"We want to reinforce in the text the idea that the International Atomic Energy Agency concentrates on its technical task and moves away from its political role," he said.

The United States had been adamant that Tehran cooperate with the IAEA to clear up suspicions about earlier work at three undeclared sites.

In June, the IAEA's board of governors adopted a resolution censuring Iran for failing to adequately explain the previous discovery of traces of enriched uranium at three sites not declared by Tehran as having hosted nuclear activities.

On Monday, President Ebrahim Raisi said reviving the atomic deal would be pointless unless the UN nuclear watchdog put an end to its probe of three undeclared sites in the Islamic republic.

The 2015 accord between Iran and six world powers -- Britain, China, France, Germany, Russia and the United States -- gave Tehran sanctions relief in exchange for curbs on its nuclear programme.

Formally known as the Joint Comprehensive Plan of Action, the agreement aimed to prevent Iran from developing a nuclear weapon -- something it has always denied wanting to do.

But the US unilaterally withdrew from the deal under then president Donald Trump in 2018 and proceeded to reimpose biting sanctions, prompting Tehran to pull back from its own commitments.

Last week, amid rising hopes of a revived deal, IAEA chief Rafael Grossi in an interview with CNN rejected the idea of the agency closing its probe on the undeclared sites without receiving answers.

"When it comes to guarantees, resolving outstanding issues related to the IAEA is also of serious concern to us," Amir-Abdollahian said on Wednesday.

"If we can reinforce the existing text, reaching an agreement will not be far from being achieved," he added.