The head of the United Nations’ nuclear watchdog has issued one of the starkest warnings to date on the growing complexity and danger posed by Iran’s nuclear program, revealing that key facilities are buried so deep underground they are beyond the reach of a single military strike.
In a candid and sobering interview with The Financial Times, Rafael Grossi, Director-General of the International Atomic Energy Agency (IAEA), described how Iran’s most sensitive nuclear installations — particularly those associated with uranium enrichment — are entrenched hundreds of meters below ground, in some cases up to half a mile (800 meters) deep.
“The most sensitive things are half a mile underground — I have been there many times,” Grossi stated. “To get there you take a spiral tunnel down, down, down.” The image he evokes is one of a hidden fortress, a labyrinthine descent into a fortified complex designed not just to enrich uranium but to withstand the most powerful of aerial assaults.
Grossi’s stark revelations come at a time of heightened regional anxiety and growing uncertainty about the future of diplomacy between Tehran and the West. With the 2015 Joint Comprehensive Plan of Action (JCPOA) effectively defunct and negotiations stalled, the prospect of military confrontation looms larger than it has in years.
“Iran doesn’t have a nuclear weapon at this moment,” Grossi emphasized, “but it has the material.” This statement aligns closely with assessments from Western intelligence agencies, which have warned that Tehran has enriched enough uranium to be within striking distance of weaponization — should it make that political decision.
According to IAEA data, Iran has accumulated enough uranium enriched to 60% purity that, if further refined to weapons-grade levels (around 90%), could be used for multiple nuclear warheads. The IAEA has expressed growing concern over Iran’s lack of transparency and cooperation, especially after the Islamic Republic significantly curtailed its compliance with the JCPOA following the U.S. withdrawal from the deal in 2018.
Further complicating international oversight, the IAEA has admitted it does not have full visibility over the current locations and activities of Iran’s advanced centrifuges, many of which are capable of rapid enrichment. These components — key to Iran’s ability to develop a bomb — have been dispersed and concealed throughout the country, often in hardened, deeply buried facilities.
While Israel has long maintained that it will not allow Iran to become a nuclear weapons state, the technical and logistical realities of a military strike are daunting. Iran’s enrichment infrastructure is not concentrated in a single vulnerable location but spread across several fortified sites, including the well-known Natanz Fuel Enrichment Plant and the Fordow Fuel Enrichment Plant.
The Fordow site, in particular, presents a formidable challenge. Buried under a mountain, the facility was specifically engineered to resist even the most sophisticated bunker-buster bombs. Although Israel possesses U.S.-supplied 5,000-pound “bunker buster” bombs, military analysts widely agree that these would not be sufficient to destroy deeply entrenched sites like Fordow in a single strike.
“[Israel] doesn’t have enough 5,000 pounders,” noted retired U.S. Air Force General Charles Wald, now a senior fellow at the Jewish Institute for the National Security of America. “They would have to go back multiple times, and every time they go back the risk increases.”
In contrast, the United States retains the ability to deploy the 30,000-pound Massive Ordnance Penetrator (MOP) — the only known conventional weapon capable of reaching the depths required to destroy the most fortified Iranian installations. These are typically deployed from B-2 stealth bombers, some of which have recently been forward-deployed to Diego Garcia in the Indian Ocean, in what experts interpret as a not-so-subtle signal to Tehran.
Even with U.S. involvement, any operation to degrade Iran’s nuclear infrastructure would be a complex, multi-day effort, involving dozens — possibly hundreds — of air sorties, electronic warfare, cyberattacks, and coordination across multiple fronts.
“A joint U.S.-Israeli operation would have a greater chance of success,” Wald acknowledged, “but even then, we are talking about buying time — not solving the problem.”
This sentiment is echoed by many nuclear policy experts who warn that military force can delay but not dismantle a country’s nuclear ambitions.
“Scientific knowledge cannot be bombed,” said Eric Brewer of the Nuclear Threat Initiative, a former intelligence official specializing in nuclear nonproliferation. “A strike might set Iran back by a year or two, but the risk is that it galvanizes rather than dissuades.”
Indeed, the unintended consequences of a military option loom large. Kelsey Davenport of the Arms Control Association warns that after a strike, Iran would likely harden its facilities even further and accelerate its program in retaliation.
“What happens the day after?” she asked. “You could trigger exactly the scenario you’re trying to avoid — a nuclear-armed Iran moving underground, out of reach, and out of sight.”
Iranian officials have already threatened to expel IAEA inspectors and halt cooperation with international monitoring efforts if external threats escalate or military action occurs.
Ali Shamkhani, a senior adviser to Supreme Leader Ayatollah Ali Khamenei, issued a veiled threat on social media last week, stating that “continuation of external threats and Iran being in a state of military attack may lead to deterrent measures, including expulsion of inspectors from IAEA and cessation of cooperation.”
This tactic closely resembles the path taken by North Korea in the early 2000s. After being accused of violating nuclear agreements, Pyongyang expelled IAEA inspectors, withdrew from the Nuclear Non-Proliferation Treaty (NPT), and successfully conducted nuclear tests by 2006.
“If you bomb Iran, Iran is going to almost certainly, in my judgment, chuck out international inspectors and make a dash for the bomb,” warned James Acton of the Carnegie Endowment for International Peace.
In essence, a military strike — even if successful in damaging infrastructure — could push Iran across the nuclear threshold in retaliation.
Perhaps most alarmingly, any military action against Iran could ignite a broader regional war. The Middle East is already reeling from the effects of multiple, overlapping crises: Israel’s continued conflict with Hezbollah in Lebanon, instability in Iraq and Syria, the Gaza war, and Houthi missile attacks in the Red Sea threatening global shipping.
Iran’s close ties with proxy forces throughout the region — including Hezbollah, the Houthis, and various Shia militias — mean that a strike on its nuclear facilities would almost certainly trigger a retaliatory response on multiple fronts. Israeli cities could come under missile barrages from Lebanon, U.S. forces in Iraq and Syria could be targeted, and the Strait of Hormuz — through which 20% of the world’s oil passes — could be closed off by Iranian naval forces.
This potential for escalation is not lost on Washington or its allies. Even hawkish voices within the U.S. military establishment acknowledge the enormity of the risk.
“A strike is not a silver bullet,” one Pentagon official told The New York Times anonymously. “It’s a Pandora’s box.”
Despite the dire warnings, there is still a faint glimmer of hope that diplomacy could regain traction. Backchannel talks have reportedly continued between Iran and European mediators, but Tehran has made the lifting of all sanctions a precondition for further negotiation — a non-starter for many in Washington.
The Biden administration, while maintaining a posture of strategic ambiguity, has not ruled out the use of force but remains focused on diplomatic solutions. However, with U.S. elections on the horizon and Israel growing impatient, time may be running out.
“The Iranian thing has incredible potential to become catastrophic,” Grossi warned. “If there is a failure in negotiation, this will imply most probably military action.”
His words are not just a reflection of political analysis, but a chilling technical assessment based on years of direct inspection and intimate knowledge of Iran’s nuclear infrastructure.
The world stands at a precipice. The revelations from Rafael Grossi are not merely insights into the depth of Iran’s nuclear tunnels; they are metaphors for how far the crisis has already sunk. As each side digs in — Tehran into mountains and hardened silos, and the West into diplomatic trench lines and military contingencies — the space for compromise narrows.
Military options remain on the table, but they are laden with peril and promise no permanent solution. Iran’s scientific base is intact, its motivation undimmed, and its regional networks robust. Any strike might buy time, but the price could be incalculable.
