WASHINGTON/LAUSANNE - Iran and world powers reached a framework agreement on Thursday on curbing Tehran’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 an atomic bomb and in return lift economic sanctions on the Islamic Republic.

Speaking at White House, President Barack Obama said the tentative agreement to contain Iran’s nuclear weapons programme is “a good deal,” arguing that it is the best option for heading off another war in the Middle East or a nuclear arms race in the region.

“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, and 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 good will 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 Mogherini, who has s acted as a coordinator 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.”

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 30.

Western countries say enriched uranium can be used to make a weapon, which they aim to prevent. 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.

Zarif said that other realms 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.

Speaking at the White House Rose Garden, Obama said the outlined agreement would “cut off every pathway that Iran could take to develop a nuclear weapon.”

“If this framework leads to a final, comprehensive deal, it will make our country, our allies, and our world safer,” Obama said. “This has been a long time coming.”

“It is a good deal, a deal that meets our core objectives,” Obama said.

One part of the deal, international inspections that Obama called “unprecedented” in their intrusiveness, means Iran will have no way of hiding any nuclear activity that falls outside the parameters of the agreement, the president said.

“If Iran cheats, the world will know it,” he said. “If we see something suspicious, we will inspect it.” The deal is, he said, “our best option by far.”

Further talks still depend to some degree on how lawmakers respond to the outline of the deal. In less than two weeks, Congress returns to Washington from a recess and plans to take up measures both to weigh in on the merits of the deal as well as to step up sanctions on Iran.

If lawmakers approve either piece of legislation and can cobble together a two-thirds majority to override a certain veto from Obama, they could upend the delicate talks.

Meanwhile, Israel dismissed celebration of a nuclear framework deal between major powers and Iran, calling it detached from reality, and vowed to continue lobbying to prevent a “bad” final agreement.

Strategic Affairs Minister Yuval Steinitz said in a statement after the announcements in Switzerland: “The smiles in Lausanne are detached from wretched reality in which Iran refuses to make any concessions on the nuclear issue and continues to threaten Israel and all other countries in the Middle East.

“We will continue with our efforts to explain and persuade the world in hopes of preventing a bad (final) agreement.”