The UN nuclear watchdog says Iran has stopped a team of inspectors from visiting a key military site.
The International Atomic Energy Agency (IAEA) says no deal has been reached on inspecting the Parchin site, south of Tehran, despite “intensive efforts”.
The inspectors had sought to clarify the “possible military dimensions” of Iran’s nuclear programme.
Iran insists it is purely for peaceful purposes, but the West suspects the programme has military implications.
The IAEA said that after two days of talks, its team was returning from Iran without a deal on a document “facilitating the clarification of unresolved issues” in connection with Tehran’s nuclear programme.