Why Trump is suddenly threatening Iran's last untouched nuclear site

President Donald Trump is threatening to strike Iran’s deeply buried Pickaxe Mountain nuclear facility — a site the United States previously left untouched while bombing the country’s other major nuclear sites, raising new questions about what may have changed.

Estimated to lie beneath at least 100 meters of rock near Iran's damaged Natanz nuclear enrichment complex, Pickaxe was designed to replace an above-ground plant capable of assembling roughly 6,000 advanced centrifuges each year before it was destroyed in 2020.

Iran said the replacement would be larger, more modern and built "in the heart of the mountain." Analysts believe the tunnels could eventually hold a centrifuge assembly line, an enrichment plant or equipment used in certain nuclear weaponization activities.

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Yet the administration has not said whether it has confirmed that centrifuges were moved inside — or why a site left untouched during earlier attacks now warrants a strike. Military experts also disagree over whether airstrikes could destroy Pickaxe’s interior or merely seal its entrances temporarily.

The same depth that could protect Iran’s nuclear infrastructure may place Pickaxe’s main chambers beyond the reliable destructive reach of America’s most powerful conventional bunker-busting weapon. Bombing its exposed entrances could deny Iran access without destroying the facility or anything stored inside.

Trump said Tuesday that the United States would probably strike the area "pretty soon" and "very heavily."

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His warning came after The Wall Street Journal reported that Israeli intelligence believes Iran moved thousands of centrifuges into Pickaxe last fall. Trump said the transfer "may have" occurred but added that the United States did not have it "on record."

"Maybe this one they have right," Trump said. "But it’s okay. It doesn’t mean anything unless they have the material."

"We follow the material," he added.

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By "the material," Trump was referring to Iran’s enriched uranium, including uranium gas that centrifuges can further enrich to weapons-grade levels.

Before the June 2025 attacks, the International Atomic Energy Agency had verified that Iran possessed 440.9 kilograms of uranium enriched to 60%, enough, if further enriched, for approximately 10 nuclear weapons under the agency’s standard measurement.

Most of the stockpile was believed to have been held at Isfahan, with additional material at Natanz and Fordow. Inspectors have since been unable to verify its amount, condition or present location.

The Institute for Science and International Security assesses that the material remains trapped at those three sites and does not believe enriched uranium has entered Pickaxe.

The administration has not said whether the United States independently corroborated the reported Israeli assessment, whether centrifuges are being stored or installed inside Pickaxe or whether nuclear material has entered the facility.

Storing centrifuges would not make Pickaxe an operational enrichment plant. The machines would have to be installed in connected cascades, linked to electrical, ventilation and piping systems and fed uranium gas.

Satellite imagery shows continued construction but no indication that Pickaxe is operational, according to the Washington-based institute. Images from February showed Iran adding concrete, rock and reinforced structures over tunnel portals in an apparent effort to harden them against airstrikes.

Analysts also observed smaller closed-roof vehicles near the entrances that could indicate Iran was outfitting the interior. The imagery could not establish what the vehicles carried.

Spencer Faragasso, a senior research fellow at the Institute for Science and International Security, said earlier U.S. and Israeli attacks prioritized Iran’s operating enrichment program. Based on what was understood about Pickaxe at the time, he said, there was "nothing of priority" inside that warranted expending valuable deep-penetrating weapons.

"The facility is still under construction, and it’s unlikely that a centrifuge plant is operating inside there," Faragasso told Fox News Digital.

But Faragasso said centrifuges could have entered aboard covered trucks without being detected in commercial imagery, making the reported Israeli intelligence plausible but impossible for outside analysts to confirm.

The reported transfer could help explain Trump’s recent focus on Pickaxe, he said. The facility is also one of the last nuclear-related sites of its size that has not been struck.

Trump did not publicly name Pickaxe during the opening months of Operation Epic Fury. It entered his public rhetoric July 13, when conservative radio host Hugh Hewitt raised the facility during an interview.

Trump said American surveillance had detected no activity there but called Pickaxe a possible target for a "nice big fat shot right into the front door."

At the end of the interview, Hewitt urged Trump to "go get Pickaxe Mountain."

"We’re going to take out Pickaxe Mountain," Trump replied. "Tell the Iranians to be ready."

The White House could not be reached for comment for this story.

The administration has not explained whether the recent threats reflect new intelligence, an effort to deter Iran from activating the facility or a shift from destroying existing enrichment capacity to preventing Iran from rebuilding.

Whether the United States could destroy Pickaxe from the air remains disputed.

Nicole Grajewski, an assistant professor at Sciences Po and nonresident scholar in the Carnegie Endowment for International Peace’s Nuclear Policy Program, said it would be "very close to impossible" to destroy the facility through an air campaign like the one the United States carried out against Fordow.

Pickaxe is deeper and more heavily fortified, she said, and does not have a publicly confirmed structural weakness comparable to those exploited there.

Retired Air Force Brig. Gen. Robert Spalding, a former B-2 operations commander, said planners would first determine whether the mission required destroying Pickaxe’s interior or merely preventing Iran from using it.

"You assess what the goals are, and then you assess the costs associated with making something not fit for use — or destruction," Spalding said.

If destroying the facility proved infeasible, he said, the U.S. could instead deny access and prevent Iran from bringing in the personnel and equipment needed to operate it.

The institute has identified two possible ventilation-shaft locations through satellite imagery, including one it considers probable. Without internal schematics, however, analysts cannot confirm their purpose or connection to the main chambers.

Faragasso said the shafts could provide weak points for deep-penetrating weapons, although the results of an attack might remain unclear.

"The facility is not invulnerable," he said. "There are options."

"At the minimum, the tunnel entrances can be collapsed," Faragasso added, saying a strike could also send damaging shock waves into the facility.

Grajewski said collapsing the portals would prevent Iran from moving personnel or equipment in or out without first undertaking an excavation visible to American and Israeli surveillance. Any effort to reopen Pickaxe could trigger another strike.

But Iran has previously excavated entrances to missile tunnels after they were attacked, meaning keeping Pickaxe closed could require continued surveillance and repeated military action.

Grajewski said a strike could provide the U.S. with a "symbolic win" against one of Iran’s most prominent remaining nuclear-related facilities but would not eliminate the broader program.

"It is a very high-value facility," she said. "But it’s not the entirety of the Iranian nuclear program."