Iran has drastically hardened the defences around its store of highly enriched uranium, collapsing tunnels and laying explosive mines at entrances at a facility in Isfahan, according to multiple sources familiar with US intelligence assessments. The move, undertaken in recent weeks, follows President Donald Trump’s public suggestion that American forces could seize the roughly half-tonne stockpile—a quantity technically close to the threshold for several nuclear weapons. Satellite imagery and human reporting indicate that reaching the material now requires heavy excavation machinery and lengthy demining operations, even for Iranian personnel.

The fortifications appear designed to render any attempt at forcible extraction prohibitively costly and dangerous. Intelligence analysts in Washington note that the measures have made a potential military raid far more complex than it was just a month ago, raising the operational risk to an unacceptable level. Equally, the obstacles complicate any future verification or removal of the uranium should diplomacy succeed—a fact that may be precisely Tehran’s intent.

The entombment unfolds against an accelerating diplomatic track. US officials have indicated that the two sides are closing in on a framework under which Iran would surrender its enriched uranium for destruction, either on-site or after transfer abroad. Viewed from Tehran, the fortifications may serve as a deterrent hedge while negotiators hammer out final terms, a tangible signal that the material will not be yielded lightly. The country’s foreign minister, Abbas Araghchi, acknowledged that the stockpile is now “under the rubble” of collapsed tunnels, hinting at the complexity of any handover.

Whether the new physical barriers become a lasting obstacle to a deal or a bargaining lever remains uncertain. European non-proliferation analysts caution that robust, intrusive verification mechanisms will be essential to ensure that whatever lies beneath the debris matches official declarations. For now, the uranium remains entombed, a concrete reminder that, even as diplomacy inches forward, both the geography of the stockpile and the mistrust surrounding it have deepened. The episode underscores the delicate choreography of the US-Iran nuclear talks: each side moves to strengthen its position even as a historic compromise appears within reach.