Israel hasn't hit Iran's Fordo nuclear facility yet. Here's why it might.

Iran has two known underground nuclear enrichment sites, the one Israel attacked on the first day of its assault at Natanz, and another at Fordo. Both sit south of Tehran in central Iran, but Fordo has long been the Iranian nuclear facility of most concern to international monitors and experts.

Buried deep in a mountain, Fordo is where many analysts believe Iran has concealed clandestine efforts to work toward a nuclear weapons capability. There have been no reported Israeli strikes on the Fordo enrichment facility.

As recently as March, U.S. Director of National Intelligence Tulsi Gabbard said American intelligence agencies did not believe Iran was building a nuclear weapon, but Israel's military asserted hours after initiating its attack on Iran last week that the U.S. information was outdated, claiming Iran was "racing towards a nuclear bomb."

Infographic with satellite image from Planet Labs PBC, from March 19, 2025, showing the Fordo nuclear site in Iran. / Credit: © 2025 PLANET LABS PBC / AFP / Getty Images

Israel Defense Forces spokesman Brigadier General Effie Defrin claimed Friday that the country had intelligence indicating the Iranian regime "has established a secret program, within the framework of which senior nuclear scientists in Iran secretly conducted the experiments required to build nuclear weapons."

Speaking to reporters early Tuesday morning, Mr. Trump appeared to have been swayed. Asked about the assessment Gabbard delivered in March, he said: "I don't care what she said. I think they were very close to having them."

Iran's leaders have always denied any interest in building a nuclear weapon, insisting the program is for civilian purposes. But if that's obfuscation, as Israel insists, and the Iranians are close to a nuclear weapons capability, more than a decade of analysis of Iran's nuclear facilities by experts around the world suggests Fordo would be central to those efforts.

Why is Iran's Fordo nuclear site such a concern?

Two experts told CBS News in 2012 — the last time Netanyahu looked close to attacking Iranian nuclear facilities — that Fordo, buried almost 300 feet beneath a mountain and protected by significant air defenses, was the most likely location for a hypothetical nuclear weapons "breakout" program.

Fordo is "obviously for nuclear weapons hedging, to preserve centrifuges in case of an attack" on other, more vulnerable facilities, Mark Fitzpatrick, an expert on Iran's nuclear program at the London-based International Institute for Strategic Studies, told CBS News in 2012.

Israel attacked the only other nuclear facility known to house significant uranium enrichment facilities in Iran last week, causing damage at Natanz.

But the progress made at Fordo even at that stage, before the U.S.-brokered nuclear deal with Iran brought United Nations inspectors into the country, and since Mr. Trump pulled the U.S. out of that agreement during his first time, prompting an escalation of Iran's efforts, has remained unverified.

 Credit: Ufuk Celal Guzel/Anadolu via Getty Images

The U.N.'s nuclear watchdog agency, the IAEA, declared Iran non-compliant with its monitoring efforts for the first time in 20 years, just hours before Israel attacked. The lack of understanding of Iran's work at the facility has long been a concern, but those concerns have mounted in recent years, since the U.S. withdrawal from the nuclear deal spurred Iran to reduce cooperation with international inspectors and ramp-up its enrichment.

In late 2023, Manuel Herrera, a weapons non-proliferation expert with two different European think tanks, said Fordo remained "one of the main concerns regarding Iran."

"Fordo has always been a major concern because of its location and because of its size," Herrera said during a discussion with fellow Iran expert William Alberque, of the International Institute for Strategic Studies. We all knew from the beginning that Fordo was a site that aimed to enrich uranium for weapons purposes, because of its location, because of its size, because of its technical capacity. And… that the Iranians have been expanding that site and also expanding the stockpile of enriched uranium in that site, should be a concern for us, because, actually, we don't have a lot of transparency on what's going on there."

Herrera noted that, "in contrast with Natanz which is overground, Fordo is underground — it's a facility which actually has a tunnel structure."

In addition to its well-fortified location and structure, Herrera said Fordo "has always been assumed to be an enrichment plant with military purposes" due to the machinery at the site.

He noted that the Iranian regime had boasted in 2019 of installing advanced "IR-6" centrifuges at Fordo, capable of enriching uranium to higher purity levels much more quickly than most of its older equipment. In early 2023, the IAEA said it had found uranium particles at Fordo enriched to almost 84% purity, which is incredibly close to the 90% purity uranium that would be required for a nuclear weapon.

"This tells us that the Iranians at least are experimenting with this kind of uranium enriched level," Herrera said.