Satellite imagery obtained by the Associated Press on December 18 shows construction work has begun at a controversial underground Iranian nuclear facility at Fordow, the news agency said.
New work at any nuclear facility in Iran is likely to exacerbate international tensions as the outgoing U.S. administration of Donald Trump continues to exert pressure on Tehran over its nuclear and weapons programs and its activities in the region.
A photo from a week earlier obtained from Maxar Technologies reportedly shows what looks like a freshly dug foundation for a building with dozens of pillars extending into the ground that could provide anti-earthquake support.
Iran's representatives to the United Nations and officials at the International Atomic Energy Agency (IAEA) were not initially available for comment, AP reported.
“Any changes at this site will be carefully watched as a sign of where Iran’s nuclear program is headed," said Jeffrey Lewis, an expert at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies.
The head of the International Atomic Energy Agency (IAEA), Rafael Grossi, said on December 17 that if the incoming U.S. administration wanted to revive the 2015 nuclear agreement that Washington pulled out of two years ago, it would have to reach a new deal on reversing Iran's subsequent breaches.
One of the possible breaches involves the resumption, announced a year ago, of uranium-enrichment activities at Fordow.
President-elect Joe Biden has said the United States will rejoin the Joint Comprehensive Plan of Action (JCPOA) "if Iran resumes strict compliance" with the deal, which eased UN sanctions in exchange for curbs on Iran's disputed nuclear activities.
Trump exited the deal in 2018. Biden is due to be sworn in on January 20.
"I cannot imagine that they are going simply to say, 'We are back to square one' because square one is no longer there," Grossi told Reuters at IAEA headquarters on December 17.
Citing "more [nuclear] material" and "more activity, more centrifuges" and other factors, Grossi said that the question of a resumption is "at the political level to decide" and that "undoubtedly" there would have to be a second deal.
"It is clear that there will have to be a protocol or an agreement or an understanding or some ancillary document which will stipulate clearly what we do," Grossi said.
The recent construction site lies northwest of Fordow's underground facility, which is known to house uranium-enrichment technology and is built deep inside a mountain for security reasons.
A Twitter account called Observer IL recently published an image of Fordow showing the work, saying it had come from South Korea's Korea Aerospace Research Institute.
The Korean institute later acknowledged taking the photo, AP said.