Vienna: Foreign ministers from major powers began crunch talks in Vienna on Monday seeking to seal a historic nuclear deal to end a 13-year standoff, one day before a final deadline, officials said.
The United States, Russia, China, Britain, France and Germany want Iran to sharply curb its nuclear programme to make any push to acquire the atomic bomb all but impossible, in return for sanctions relief.
Iran denies wanting nuclear weapons, saying its activities are purely for peaceful purposes such as generating electricity and treating cancer patients.
The deal, capping almost two years of rollercoaster talks following the 2013 election of Iranian President Hassan Rouhani, would build on a framework accord reached in April in Switzerland.
Under that framework, Iran will reduce by more than two-thirds its uranium centrifuges, which can make nuclear fuel but also the core of a nuclear bomb, reduce its uranium stockpiles and alter its Arak reactor.
Tough issues in finalising the accord include working out the pace and timing of sanctions relief, Iran`s future capacities to develop nuclear equipment and enhanced UN access, including potentially to military bases in Iran.
On Sunday, US Secretary of State John Kerry, who has been meeting on and off for the past 10 days with his Iranian counterpart Mohammad Javad Zarif, said "it is now time" to seal the deal.
"Over the past few days we have in fact made genuine progress, but I want to be absolutely clear with everybody we are not yet where we need to be on several of the most difficult issues," Kerry said.
"While I completely agree... that we have never been closer, at this point this negotiation could go either way," he said.