US President Donald Trump has issued repeated threats to bomb an Iranian nuclear site buried deep beneath a mountain near Natanz, a facility known as Kuh-e Kolang Gaz La or “Pickaxe Mountain.” The site, under construction since 2020, is estimated by non-proliferation analysts to lie between 80 and 100 metres below the surface, and possibly deeper as excavation continues. Trump told journalists on Tuesday that American forces would strike the area “very soon and very heavily,” adding, “there’s not a thing they can do about it.” The International Atomic Energy Agency (IAEA) has never been granted access to the site, leaving its precise contents unverified.

Viewed from Washington, the threat forms part of an escalating military campaign. US forces have conducted strikes on Iran for ten consecutive days, according to US Central Command, amid a broader confrontation over shipping in the Strait of Hormuz. Trump acknowledged the possibility that Tehran had moved centrifuges into the mountain but downplayed its significance, stating that “we follow the material” — a reference to Iran’s pre-war stockpile of highly enriched uranium, which remains at previously bombed sites. US officials have reportedly discussed using two GBU-57 bunker-busting bombs in succession to penetrate the facility, though the weapon is rated to pierce only 60 metres of earth, raising questions among military analysts about its effectiveness against a target that may exceed 100 metres of rock.

Iran’s foreign ministry spokesman rejected the accusations, asserting that “no nuclear activities are taking place” at Kolang Kuh and describing Washington’s focus as a “fabricated pretext for aggression.” Tehran has warned that any attack on its nuclear installations would expand the war regionally. The IAEA’s director, Rafael Grossi, confirmed that Iran had notified the agency in 2021 of its intention to conduct nuclear activities at the site, but subsequent requests for inspections went unanswered. Satellite imagery analysed by the Institute for Science and International Security (ISIS) shows four tunnel entrances, anti-aircraft batteries, and a perimeter secured by the Revolutionary Guard, consistent with a facility designed to house centrifuge assembly or uranium enrichment.

The site was initiated after a 2020 explosion — widely attributed by Western intelligence to Israeli sabotage — destroyed an above-ground centrifuge workshop at the adjacent Natanz complex. During the 12-day war between Israel and Iran in 2025, the US bombed Natanz and the underground Fordo enrichment plant with bunker-busters, but Pickaxe Mountain was left untouched. Analysts at the James Martin Center for Nonproliferation Studies suggest the depth and ongoing expansion indicate an effort to create a hardened backup for Iran’s enrichment capabilities. The mountain’s geology and the presence of multiple tunnel levels, with a vertical separation of roughly 50 metres, complicate targeting.

Diplomatic channels remain frozen. Trump stated that the US has no interest in talks unless Iran is ready for “meaningful” negotiations, while Tehran insists on an end to strikes as a precondition. The IAEA has no inspection mandate for the site, and the status of Iran’s broader nuclear programme remains opaque following the 2025 bombardments. The next factual step is the potential execution of the threatened strike, which would mark the first direct US attack on a facility whose function and vulnerability remain matters of contested intelligence.