UN nuclear watchdog chief Rafael Mariano Grossi said Thursday that Iran’s new workshop for making machine parts for enriching uranium at Natanz was underground.

The International Atomic Energy Agency informed member states two weeks ago that Tehran had moved machines to a more secure setting from Karaj, west of Tehran, where its factory was sabotaged in June 2021 in an attack widely attributed to Israel.

Grossi told Associated Press Wednesday that the new plant, part of the larger site at Natanz where uranium is enriched, reflected the growth in Iran’s nuclear program. “The activity is not new, but the production lines, the production capacities, are being expanded,” he said.

Grossi said Wednesday that “political circumstance” should be overcome for effective UN monitoring of the Iran nuclear program to resume, stressing the agency’s work both in inspecting Iranian atomic facilities and in pursuing answers over past nuclear activities.

While the IAEA is not directly involved in Vienna talks to revive the 2015 Iran nuclear agreement, the JCPOA (Joint Comprehensive Plan of Action), Grossi has made clear the agency’s knowledge and supervision of Iran’s nuclear activities was undermined by the United States in 2018 leaving the JCPOA and Iran’s 2019 decision to reduce IAEA access and break JCPOA nuclear limits.

Tehran is due to satisfy the agency’s concerns by June 21 over work carried out before 2003 in sites where the IAEA later detected traces of uranium.