Trump may send US troops to neutralize Iran’s highly enriched uranium. There are no good options

By François Diaz-Maurin | Analysis | March 9, 2026

When Israel attacked Iran on June 13, a ten-day delay occurred before US B-2 bombers arrived to target deep underground facilities at Fordow and Natanz. This lag, caused by the need for Israel to neutralize Iranian air defenses and the United States to prepare for the operation, created a critical window for Iran. Although the United States dropped powerful bunker-buster bombs, satellite imagery and expert testimony suggest Iran may have reinforced its tunnels with concrete to shield them from the impact of the incoming strikes and used that time to move centrifuges and enriched material out of some facilities.

The aftermath has left the Trump administration facing a self-induced dilemma regarding the location and state of the remaining stockpile, particularly at the Isfahan nuclear complex. Because the facility is too deep for conventional bombing to guarantee destruction, there is growing debate over a high-stakes ground mission to seize the cylinders that contain the highly enriched uranium. Such an operation is fraught with peril, ranging from the risk of nuclear criticality and toxic chemical leaks to the tactical nightmare of operating in an active war zone. Ultimately, if the United States cannot secure or safely destroy the material buried “under the rubble,” Iran may retain a residual nuclear capability that its new leadership could retrieve and weaponize in the future.

Critical delay. Last May, the International Atomic Energy Agency (IAEA) issued a report estimating that Iran had already enriched over 400 kilograms of its uranium hexafluoride gas to 60 percent uranium 235—a level considered highly enriched, but not yet weapons grade. This material is enough for about 10 crude nuclear weapons and can be enriched further to make nuclear weapons that can fit into a ballistic missile.

Israel used the IAEA report to justify launching a military action against Iran’s nuclear weapons program on June 13. But it was not until June 22 that the United States entered, with its heavy bombers capable of destroying Iran’s underground enrichment facilities.

This delay had several explanations. Israel needed to first neutralize Iran’s air defenses and create corridors for US bombers to freely enter Iranian airspace and conduct their mission. The US military also needed time to bring its B-2 bombers in from their US bases, even using subterfuge to fake a deployment over the Pacific. Although he may have known of the general intentions of Israel, President Donald Trump claimed he was not informed by Israel’s Prime Minister Benjamin Netanyahu before the June 13 attack. Probably seeking to maintain the effect of surprise and avoid the possible pushback from the US administration, Netanyahu’s decision may have delayed the US military intervention, which was not popular among the US population and politically risky for Trump.

However necessary, Iran may have used this lapse of 10 days to smuggle critical nuclear material and equipment out of its enrichment facilities into undisclosed facilities. On June 20, even before the US attack, the former commander of Iran’s Revolutionary Guard, Mohsen Rezaei, said that the enriched nuclear material had been moved to secure locations. “We will not give up its position.” Rezaei added that all the United States could do was target the Fordow plant, which is precisely what it did.

Contested results. Before the first US attack in June, all eyes were on Fordow. The plant, located near the city of Qom, had enough centrifuges and uranium hexafluoride gas to potentially produce several nuclear weapons, making it a prime target of Israel’s effort to attack Iran’s nuclear program. But only the United States possessed the military capability of destroying the facility, whose tunnels are believed to be as deep as 80 to 90 meters.

Just hours before the US attack, satellite images dated June 19-20 and posted online showed trucks going in and out of the underground tunnel entrance at the Fordow enrichment plant, leaving experts wondering about the increase in logistics at the facility.

“This activity may suggest that Iran, anticipating a strike, has started reinforcing the facility possibly by moving in materials to strengthen tunnels or seal the site in preparation of a fallout,” said Damien Symon, a geospatial intelligence researcher. But nuclear experts were also worried that Iran may have moved centrifuges or enriched uranium out of Fordow. “It’s still a mystery exactly what was in those trucks,” said David Albright, a former UN weapons inspector who now runs the Institute for Science and International Security, which tracks Iran’s nuclear facilities using satellite imagery.

During its June attack, the United States bombed Iran’s nuclear facilities, dropping 14 of its most powerful “bunker-buster” bombs on Natanz and Fordow. The apparent success of the attack, with craters clearly visible on satellite images, prompted President Donald Trump to quickly claim that Iran’s nuclear program was “obliterated.” That claim, however, was later disputed as a classified damage assessment of the facilities was leaked to the press, suggesting that the bombs may not have reached the vaults deep underground where the centrifuges were being located.

At a press briefing on the military operation, Chairman of the Joint Chiefs of Staff Gen. Dan Caine put an end to the speculation about the trucks: “In the days preceding the attack against Fordow, the Iranians attempted to cover the shafts with concrete to try to prevent an attack.” The trucks visible on satellite imagery were dump trucks, not trailers capable of transporting sensitive equipment or nuclear material. Trump himself posted, “Nothing was taken out of facility.”

In September, as negotiations were underway with the IAEA on how to restore inspections and avoid further attack, Iranian Foreign Minister Abbas Araghchi seemed to confirm the US assessment when he claimed that Iran’s enriched nuclear material was “under the rubble” of the damaged facilities. But to experts, the doubt remained. “Any highly enriched uranium at Fordow was likely gone before the attack,” Albright said in June.

Rafael Grossi, IAEA’s director general, also said following the June strikes that some highly enriched uranium could have been moved before the attack. “If we don’t get that clarification, this will continue to be hanging over our heads as a potential problem.”

Consolidation at Isfahan. In June, the US military did not use bunker-buster bombs on Isfahan, Iran’s third-largest nuclear complex. The facility is built so deep that the US military estimated its bombs would not have been able to reach the centrifuges. Instead, the United States used Tomahawk missiles launched from a US submarine to attack the tunnel entrances, which Iran had preemptively filled and sealed with dirt.

Less than a week after the June bombings, however, satellite images showed that Iran had already cleared at least one of the tunnel entrances at Isfahan. A truck was spotted accessing the entrance, prompting suspicions that Iran may have attempted to retrieve some of its enriched uranium that may have been stored in the tunnels. But it could also be the opposite, with Iran attempting to place nuclear material inside the undamaged facility.

By all likelihood, the buildings and tunnel shafts that the United States bombed did not contain highly enriched uranium, or if they did, at least the cylinders were not damaged. The IAEA said that no increase in radiation levels was measured outside of the damaged facilities following the June strikes, although toxic chemicals and radiological contaminants may have been dispersed inside some of these facilities.

Two things may be true at the same time: Part of the enriched uranium had probably been removed ahead of the June strikes, while another part may have been left on sites at Fordow and Natanz, buried deep enough to be out of reach of even the most powerful US bombs. “Under the rubble” could just mean (temporarily) inaccessible, not necessarily destroyed and dispersed. And others doubt it is even the case at Isfahan. “I have never understood the rubble comment,” Richard Nephew, an expert on Iran, wrote on X. “Yes, maybe at Natanz and yes maybe at Fordow, but it was not this at Isfahan and has not been this at Isfahan.”

Various reports indicated new activity was happening at the site, including vehicles entering Isfahan’s tunnel entrances. Satellite images indicate that, by early February, all entrances to the Isfahan tunnel complex had been completely backfilled and buried with soil. This suggests that Iran may have placed all or part of its remaining stockpile of highly enriched uranium inside the underground facility, in an attempt to protect it against possible air strikes or ground operations. On March 7, the New York Times reported that trucks were removing dirt from another tunnel entrance. But experts doubt that the tunnel in question is physically connected to the Isfahan nuclear complex by an underground passageway.

US officials dismissed the possibility that Iran may be successfully smuggling out any material undetected, given the constant surveillance the site receives from US intelligence agencies. Still, doubt will remain about the fate of the nuclear material at Isfahan, which experts believe now holds much, if not most, of Iran’s highly enriched uranium. Even if not removed now, the stockpile of highly enriched uranium is already de facto in the hands of Iran’s Islamic Revolutionary Guard Corps (IRGC), now that Iran named Mojtaba Khamenei, Ayatollah Ali Khamenei’s son, who has strong ties with the IRGC, as its new supreme leader. The question is now whether the United States can prevent the Iranians from ever digging it out again.

Risks of a ground operation. The situation at Isfahan shows the limits of a strategy by the US administration, which thinks it can bomb Iran’s nuclear program away. Despite repeated claims by US officials that the United States is not at war with Iran and that there will be no boots on the ground, President Trump is now reportedly considering sending US troops for “specific strategic purposes,” including to seize Iran’s stockpile of enriched uranium. But this idea comes with significant chemical, logistical, and tactical hurdles.

Iran’s highly enriched uranium is likely stored as uranium hexafluoride gas in heavy metal cylinders. Cheryl Rofer, a former radiochemist at Los Alamos, estimates that the 400 kilograms of Iran’s highly enriched uranium would require anywhere between 30 and 60 cylinders. Because it is highly enriched in fissile uranium 235, cylinders would have to be carefully stored in small quantities separated from one another to prevent sparking nuclear criticality. (Criticality happens when neutrons emitted by fissile material generate a spontaneous self-sustaining fission chain reaction.)

Hurried transport under improper conditions could also lead to exposure to toxic chemicals. For instance, if moisture enters transport or storage cylinders, uranium hexafluoride will react with the water content to produce highly toxic hydrofluoric acid gas and solid uranyl fluoride aerosol particles. This could potentially lead to the rapid leakage and dispersion of contaminants out of the cylinders, posing an extensive chemical toxicity hazard.* Removing this material would require Special Operations Forces, along with technicians specially trained in handling nuclear material. The US Army’s 20th Chemical, Biological, Radiological, Nuclear, Explosives (CBRNE) Command has three special units called Army Nuclear Disablement Teams trained to disable any potential enemies’ nuclear capabilities. But their missions are to dismantle and destroy nuclear materials and programs, not transporting it away.

Logistically and tactically, this mission would be highly perilous, if not nearly impossible. Isfahan is located several hundred miles from the nearest US naval ships, requiring long-range transport through an active war zone. The US and Israeli air forces could provide air superiority to allow troops and equipment in and out of Isfahan. But special forces on the ground would still need to pass through Iranian security forces and bring in heavy equipment to dig the material out of tunnels, potentially damaged and filled with debris. Such a mission would last probably several days, exposing US personnel to possible attacks, not to mention the possibility that the site may be booby-trapped.

An obvious alternative to seizing the enriched uranium would be to destroy the cylinders directly on site. This option would have the advantage of effectively neutralizing the stockpile while avoiding the logistical problems and associated risks to US personnel. But exploding the stockpile would chemically contaminate the immediate surroundings with toxic uranyl fluoride, creating a lasting environmental hazard. Moreover, there would be the problem of assessing the damage: Doubt will always remain as to whether all the cylinders are destroyed and uranium is widely dispersed, or if Iran could retrieve enough of it for a nuclear weapon after US troops leave. (This problem of damage assessment would be even worse if US forces attempted to destroy the material by air strikes without sending special operations forces, as the military would not know exactly how much nuclear material is being stored, assuming bombs can even reach the stockpile.)

Now that the United States has chosen the military option and Iran has all the incentives to rush toward building a nuclear weapon, Iran’s stockpile of highly enriched uranium has created a self-induced dilemma for the Trump administration: If not properly dealt with, the nuclear material will give whoever is in power after the war “a residual nuclear weapons capability,” Albright said.

(March 17, 2026): * This sentence was edited after posting to correct for the fact that the reaction of uranium hexafluoride with water vapor may not lead to the explosion of cylinders, but rather to the leakage of toxic chemical contaminants in the form of a high-velocity jet.