Iran said yesterday it had offered ways to address foreign concerns over its underground Fordow uranium enrichment plant, hinting at flexibility on a serious obstacle to a nuclear deal with big powers as a self-imposed July 20 deadline nears.

It was not immediately clear whether the Iranian suggestions were far reaching enough to bridge the gap over Fordow, one of a handful blocking progress towards a long-term agreement that would improve stability in a Middle East riven by conflicts.

None of the outstanding issues in talks has been settled

France, one of the powers, had said on Tuesday that none of the main outstanding issues in the talks, including Fordow, had been settled and that the US wanted foreign ministers to join in to help overcome deadlocks.

The US, Russia, France, Germany, China and Britain want to cap Iran’s capacity to enrich uranium to ensure Iran cannot accumulate potential fuel for atomic bombs. In return, Iran would be rid of sanctions crippling its economy.

Iran denies any intention to derive bomb material from enriched uranium or that it is seeking the technical know-how and means to assemble a nuclear weapon. It says it wants to refine uranium only for civilian energy purposes.

Western powers have in the past called on Iran to shut down Fordow, regarding the plant – built in a fortified bunker deep underground and protected by anti-aircraft batteries – as ideally suited to enriching uranium to weapons-grade.