Head of United Nations' nuclear watchdog has raised concern about Iran's nuclear program and the regime’s sluggish cooperation with the agency.

In an interview with France 24, the Director General of the International Atomic Energy Agency (IAEA) Rafael Grossi said, "Iran's continuing enrichment activities, it's raising concerns.”

Nevertheless, he said, "we agreed that Iran collaborates with the agency, limiting some activities, allowing us to add more monitoring capacities," adding however that “Our deal with them for more verification isn't working to the level and pace I would like to see."

Referring to an agreement he reached with Iran in March, Grossi said, “We have been able to do some of that, not all of that," he said, noting that “Iran in continuing its enrichment activities.”

Since the last time Grossi was in Iran and announced new agreements with the regime three months ago, Iran's stockpile of enriched uranium has increased by more than a quarter.

Earlier in June, Iran said it has reinstalled 10 cameras of the UN nuclear watchdog in one of its installations that were removed last year when the UN watchdog’s board of governors in June 2022 censured Tehran for its lack of cooperation with the agency.

Grossi also welcomed unconfirmed reports that US President Joe Biden’s administration seems to favor an informal and unwritten agreement with Tehran following the collapse of Vienna talks to restore the 2015 nuclear deal -- the Joint Comprehensive Plan of Action (JCPOA).

"I'm aware of bilateral contacts between Iran and the US... If there is any alternative kind of agreements, I hope we will be invited to verify that whatever commitments are taken are for real, and not just a piece of paper," he added.