US Secretary of State John Kerry arrives on crutches to deliver a statement on Cuba outside the hotel where the Iran nuclear talk meetings are being held in Vienna, Austria, on July 1, 2015. Source: AFP

International Atomic Energy Agency chief Yukiya Amano was to hold talks in Tehran, seeking a way around one of the thorniest issues in the long-running talks: a stalled probe into Iran’s suspected nuclear bomb development.

The foreign ministers of France, Germany, Britain and China were expected to join the main talks in Vienna, where US Secretary of State John Kerry and Iran’s Mohammad Javad Zarif have been locking horns since Saturday.

EU foreign policy chief Federica Mogherini will also take part. It was unclear if Russian Foreign Minister Sergei Lavrov will also return to the Austrian capital.

“We are working very, very hard and we have some very difficult issues,” Mr Kerry said on Wednesday, a day after the deadline for a deal was extended to July 7.

“But we believe we’re making progress and we’re going to continue to work because of that.”

Mr Amano’s visit to Tehran at Iran’s invitation, where he will meet President Hassan Rouhani, is aimed at jump-starting a stalled probe into allegations of suspicious nuclear activity by Iran.

The P5+1 powers — the US, Russia, China, Britain, France and Germany — want Iran to co-­operate in the investigation, saying it is a vital piece of the mooted accord.

But Iran rejects the allegations that its nuclear program had “possible military dimensions” saying they were based on bogus intelligence provided by the CIA and Mossad.

It also baulks at the desire of the IAEA — which it sees as biased and riddled with spies — to visit military sites such as Parchin and interview its scientists.

One possible compromise might be strictly controlled “managed access” visits that reassure Iran that IAEA staff are not spying under the guise of inspections, experts say.

The hoped-for accord, after ­almost two years of negotiations and 13 years of rising tensions, ­focuses more on the future rather than the past, however.

Under a framework deal from April, Iran will scale back its nuclear activities with the aim of putting the development of an atomic bomb beyond its reach. In return painful sanctions would be progressively lifted.

Finalising the framework agreement from Lausanne has proved difficult. Tough issues ­include the timing of sanctions ­relief, the mechanism for their “snapback” and Iran’s development of nuclear equipment.

AFP