Iran Defies Nuclear MOU With Continued Underground Construction, Watchdog Warns

The Institute for Science and International Security said this week that Iran is sustaining construction at a secret underground nuclear site in the Zagros Mountains, undermining the memorandum of understanding Tehran signed with the Trump administration and raising fresh doubts about the viability of ongoing negotiations. International Atomic Energy Agency inspectors have not been granted access to the facility, known as Pickaxe Mountain. The disclosure comes months after the United States and Israel launched Operation Epic Fury on Feb. 28, 2026, targeting Iran's nuclear and missile capabilities.

IAEA Locked Out as Tunnel Work Presses On

The Washington-based Institute for Science and International Security published a detailed analysis of new satellite imagery from late June 2026 showing continued vehicle activity on roads leading to tunnel portals at Pickaxe Mountain. The institute said the imagery indicates construction inside the tunnel complex is ongoing, along with hardening of the tunnel entrance.

Spencer Faragasso, a senior ISIS fellow covering Iran, North Korea, illicit trade, and nuclear issues, wrote on X that the activity has continued steadily since at least 2020. He described the work as a hedge by Iran in case negotiations collapse, and assessed the facility as likely large enough to hold a uranium enrichment plant. Faragasso called for Iran to halt construction at the site as a minimum good-faith measure, framing it as a test of whether Tehran intends to break from what he characterized as a pattern of deception.

The MOU signed between the United States and Iran requires Tehran to maintain the status quo, a condition the institute said plainly prohibits construction at any nuclear-related facility, including Pickaxe Mountain. Iran has previously used facilities at Natanz, Fordow, and Isfahan to enrich uranium, the key material in a nuclear weapons program. In late June, the IAEA declined to respond to a detailed query on whether it would seek access to the site.

Damaged Sites Sit Idle While Fordow Adds Passive Defenses

Satellite imagery reviewed by ISIS presents a mixed picture at Iran's other known nuclear installations. At Natanz, little activity was visible; access points to below-ground enrichment halls remain unrepaired, personnel entrances remain destroyed, and vehicle entrances remain severely damaged. A covering was noted over the remains of the Pilot Fuel Enrichment Plant, which was destroyed in June 2025. At Esfahan, ISIS reported no observed activity as of June 29, 2026, with tunnel portals backfilled with dirt.

At Fordow, buried inside a mountain north of the Islamic holy city of Qom, Iran moved between May 10 and May 18 to add passive defensive measures. The institute said earthen and rocky mounds and other objects were placed along roads leading to tunnel entrances in precise alternating arrangements, forming a series of chicanes. ISIS assessed the configuration as designed to restrict rapid vehicle movement toward the tunnels rather than to block access outright. A June 21 satellite image showed those objects still in place, with Fordow's tunnel portals continuing to sit backfilled.

Pressure Mounts on Negotiating Framework

Fox News Digital sent questions to the State Department and the Iranian Mission to the United Nations. Neither had responded publicly at the time of the institute's report. ISIS argued that halting work at Pickaxe Mountain and permitting IAEA inspections would represent the baseline proof needed to determine whether Iran is prepared to abandon its documented history of nuclear concealment — and that absent those steps, the MOU's status-quo requirement remains effectively unenforceable.