The two-day visit by the head of the International Atomic Energy Agency (IAEA) comes as the Vienna-based organisation seeks greater cooperation with Iran over its nuclear activities.

"By having a constructive discussion... and having good agreements, like I am sure we are going to have, we are going to be paving the way for important agreements," Grossi told a news conference alongside Iran's top nuclear official Mohammad Eslami.

Grossi arrived Friday in Iran amid deadlock in negotiations on reviving a landmark 2015 accord on Iran's nuclear activity, known formally as the Joint Comprehensive Plan of Action, or JCPOA.

A diplomatic source told AFP that Grossi would meet President Ebrahim Raisi to "relaunch the dialogue" on Iran's atomic work and to "reset the relationship at the highest level".

Grossi had previously made clear "that he was only prepared to go to Tehran if he had an invitation to speak with the president," the source added.

Uranium particles enriched up to 83.7 percent -- just under the 90 percent needed to produce an atomic bomb -- had been detected at Iran's underground Fordo plant about 100 kilometres (60 miles) south of Tehran, according to a confidential IAEA report seen by AFP this week.

Iran denies wanting to acquire atomic weapons, and says it had made no attempt to enrich uranium beyond 60-percent purity.

Iran's government has said, however, that "unintended fluctuations... may have occurred" during the enrichment process.

The discovery came after Iran had substantially modified an interconnection between two centrifuge clusters enriching uranium, without declaring it to the IAEA.

- 'Obligations' -

On Saturday, Eslami, who heads the Atomic Energy Organization of Iran, called on all parties to the 2015 deal to fulfil their "obligations".

"Three European and some other countries are just focusing on Iran's JCPOA obligations," he told the news conference. "They too have obligations that they need to adhere to."

"We came to an arrangement (with Grossi) to define our cooperation within the framework of the safeguards" on nuclear activity, he added.

"The relevant authorities will make a decision" if a resolution is reached, and Iran's atomic agency will adhere to that decision, he said.

"Iran never sacrifices its national interests for anything else," Eslami said.

Depending on the outcome of Grossi's trip, the US as well as Britain, France and Germany will decide whether to submit a draft resolution censuring Iran to the IAEA board of governors, which is due to convene next week in Vienna.

Grossi also met on Saturday with Iranian Foreign Minister Hossein Amir-Abdollahian, the official news agency IRNA reported.

And during his visit he aimed to secure "more access to the (Fordo) site, more inspections," the diplomatic source said.

- 'Greater cooperation' -

The 2015 deal between Iran and world powers promised Tehran relief from biting economic sanctions in exchange for curbs on its nuclear activities.

The restrictions set out in the deal, including the 3.67-percent enrichment threshold, were intended to prevent Iran from developing a nuclear weapon.

The United States unilaterally withdrew from the pact in 2018 under then-president Donald Trump and reimposed sanctions, prompting Iran to suspend the implementation of its own commitments.

Negotiations aimed at reviving the deal started in 2021 but have been stalled since last year.

Grossi's visit is being seen in Iran as another indication that a dialogue-based approach to resolving the nuclear standoff is possible.

"It is hoped that this trip will form the basis for greater cooperation and a clearer horizon between Iran and the IAEA," the spokesman of Iran's atomic agency Behrouz Kamalvandi said ahead of Grossi's visit.

In November 2022, Western nations criticised Iran for its lack of cooperation after traces of enriched uranium were found at three undeclared sites.

Grossi, who last visited Iran in early March 2022, is due to hold a news conference upon his return to Vienna late Saturday afternoon.