The visit by International Atomic Energy Agency head Rafael Grossi is seen as critical to clinching a return to the nuclear agreement, and comes parallel to negotiations in the Austrian capital.
The head of the United Nations' nuclear watchdog has met with Iranian officials as talks in Vienna over Tehran's tattered atomic deal with world powers appear to be reaching their end.
Rafael Mariano Grossi of the International Atomic Energy Agency described Saturday's visit to Tehran as a means “to address outstanding questions" as negotiators back in Europe appear to be reaching a deadline to see if the 2015 accord can be revived.
“This is a critical time but a positive outcome for everyone is possible,” Grossi wrote on Twitter ahead of his flight on Friday.
Grossi arrived on Saturday to a meeting with Mohammad Eslami, the head of the civilian Atomic Energy Organization of Iran. He was expected to later see Iranian Foreign Minister Hossein Amirabdollahian.
“It is expected that the issues between us and the agency in general will be reviewed and about how we will pursue different issues in the future," Behrouz Kamalvandi, an AEOI spokesman, told Iranian state television earlier on Saturday. "God willing, there will be an understanding.”
Tehran's growing uranium stockpile
The latest round of talks have been taking place in the Austrian capital since late November, along with counterparts from China, Iran and Russia and the United States participating indirectly.
The so-called Joint Comprehensive Plan of Action (JCPOA), signed in 2015, secured sanctions relief for Iran in return for strict curbs on its nuclear program.
It began unravelling when then US President Donald Trump withdrew in 2018 and re-imposed sanctions, prompting Iran to start disregarding the limits on its nuclear activity.
Iran’s stockpile of enriched uranium has now reached more than 15 times the limit set out in the 2015 accord, the UN's IAEA nuclear watchdog said earlier this week.
Several observers believe that the West could leave the negotiating table and chalk the deal up to a failure if a compromise is not reached by this weekend.
Grossi is expected to hold a press conference on his return to Vienna.