The US Secretary of State John Kerry has declared that Iran has backed out of a deal on its nuclear programme during talks with world powers in Geneva on Saturday.

According to source, Mr. Kerry said "The P5+1 were unified on Saturday when proposal were presented to the Iranians, but Iran couldn't take it, at that particular moment. “They weren't able to accept it’’, he said.

Mr Kerry has however sought to reassure Israel and Gulf Arab states close to Washington that they would not be abandoned in the wake of a nuclear deal with Iran.

"We will stand up for and defend our allies in this region against any kind of external threat," he said.

Diplomats have also said that the Iranian government's insistence on formal recognition of its "right" to enrich uranium had been the major obstacle to an agreement.

Mr Kerry said he hoped in the next few months they could "find an agreement that meets everyone's standards".

Representatives from Iran and the so-called P5+1 - the US, UK, France, Russia and China plus Germany - will meet again.