Iran and world powers reached a framework agreement on Thursday evening on curbing Iran's nuclear programme for at least a decade after eight days of marathon talks in Switzerland.
The tentative agreement clears the way for talks on a future comprehensive settlement that should allay Western fears that Iran was seeking to build a nuclear bomb and in return lift economic sanctions on the Islamic Republic.
US President Barack Obama said in a statement the outcome was a good deal, comparing it to nuclear arms control deals struck by his predecessors with the Soviet Union that “made our world safer” during the Cold War.
"Today, the United States, together with our allies and partners, has reached an historic understanding with Iran, which if fully implemented will prevent it from obtaining a nuclear weapon," he declared.
Under the outline deal, Iran would shut down more than two-thirds of its centrifuges producing uranium that could be used to build a bomb, dismantle a reactor that could produce plutonium and accept intrusive verification.
"Today we have taken a decisive step, we have reached parameters," EU foreign policy chief Federica Mogherini told a news conference. "The political determination, the goodwill of all parties made it possible.
"This is a crucial decision laying the agreed basis for the final text of joint comprehensive plan of action. We can now start drafting the text and annexes," said Ms Mogherini, who has acted as a co-ordinator for the six powers - Britain, China, France, Germany, Russia and the United States.
The framework, fiercely opposed by US ally Israel, includes limits on Iran's enrichment of uranium for 10 years.
Iran's foreign minister Javad Zarif cautioned, however: "We're still some time away from reaching where we want to be."
Comprehensive settlement
A Western official said the sides had agreed that the comprehensive settlement would require Iran to dilute or ship abroad most of its stocks of enriched uranium, and leave just 6,000 out of the 19,000 centrifuges it operates for enrichment.
The deal wrapped up eight days of talks, extended after a deadline of midnight on Tuesday, aiming to achieve a political accord that could serve as the basis of a final deal by June 30th.
Western countries say enriched uranium can be used to make a weapon, which they aim to prevent happening in Iran. Iran says it wants it only for a peaceful nuclear energy programme.
The talks were the biggest opportunity for rapprochement between Washington and Tehran since they became enemies after Iran's 1979 revolution, but any deal faces scepticism from conservatives in both countries. US allies in the Middle East are also sceptical, especially Israel and Saudi Arabia.
Mr Zarif said other areas of Iran and US relations had nothing to do with the agreement.
“This was an attempt to resolve the nuclear issue...We have serious differences with the United States,” he said.
“We have built mutual distrust in the past... So what I hope is that through courageous implementation of this, some of that trust could be remedied. But that is for us all to wait and see.”
Reuters