LAUSANNE: Iran and world powers reached a framework agreement on Thursday 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 an atomic 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.

Obama welcomed the “historic understanding” with the Islamic republic after decades of hostility, but cautioned that more work needed to be done.

“If Iran cheats, the world will know it,” he said in a televised address from the White House.

Hundreds of Iranians took to the streets of Tehran in celebration after the agreement was announced, with drivers sounding their horns in approval along the capital's longest street, Val-e-Asr Avenue.

But Iran's arch-foe Israel said it would increase the risks of nuclear proliferation and of “a horrific war”, with Israeli Prime Minister Benjamin Netanyahu telling Obama the deal “would not block Iran's path to the bomb. It would pave it,” according to an Israeli spokesman.

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.

Iranian caution

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. “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.”

'Big day'

US Secretary of State John Kerry hailed a “big day”, while Iranian President Hassan Rouhani said the drafting of a full accord would begin immediately with the aim of completing it by the June 30 deadline.

EU foreign policy chief Federica Mogherini said the United States and the EU will lift all nuclear-related sanctions on Iran once the UN atomic agency has verified that Tehran has stuck to the ground-breaking deal.

And the US said all past UN nuclear resolutions on Iran would also be lifted.

Kerry said Iran's stocks of highly enriched uranium will be cut by 98 per cent for 15 years, while its unfinished Arak reactor will not produce weapons-grade plutonium.

The Fordo facility, built deep into a mountain, will remain open, however will not be used for enrichment but for research and development.

The deal will also see Iran reduce by roughly two-thirds — to 6,104 from around 19,000 — the number of uranium centrifuges, which can make fuel for nuclear power but also the core of a nuclear bomb.

Iranian negotiators had been under pressure from domestic hardliners not to give too much away while also delivering on Rouhani's promise to win the lifting of sanctions.

The so-called P5+1 group — the United States, Britain, China, France and Russia plus Germany — hope that the deal will make it virtually impossible for Iran to make nuclear weapons.

Iran, one of the world's major oil producing countries, has always denied seeking the atomic bomb, saying its activities are for energy generation and research.

'Sanctions can be reimposed'

France, which has taken a hawkish line during the negotiations, warned that sanctions could be reimposed if Tehran does not fully keep its side of the bargain.

“Sanctions that are lifted can be reimposed if the deal is not applied," President Francois Hollande's office said in a statement, adding that Paris would watch closely to ensure a “credible” and “verifiable” final agreement that prevents Iran from developing a nuclear weapon.

German Chancellor Angela Merkel said the international community had never “been so close to an agreement preventing Iran from having nuclear weapons”.

Russia, which built Iran's nuclear power plant, hailed the deal as a recognition of Tehran's “unconditional right” to pursue a civilian nuclear programme.

“A comprehensive, negotiated solution to the Iranian nuclear issue will contribute to peace and stability in the region and enable all countries to cooperate urgently to deal with the many serious security challenges they face,” UN chief Ban Ki-moon said in a statement.

The Russian foreign ministry also said the framework deal would have “a positive impact” on the security situation in the Middle East.

Successful implementation of the deal could put Iran and the United States on the road to better relations after 35 years of animosity since the 1979-1981 hostage crisis in Tehran.

US analyst Daryl Kimball of the Arms Control Association said the parameters agreed so far could “lead to one of the most consequential and far reaching nuclear nonproliferation achievements in recent decades”.

Obama needs a deal which he can sell to hostile Republicans in Congress, who remain suspicious of Iran's pledges and are threatening to push for new sanctions from April 14.

Crude oil prices fell in New York after the framework accord was announced, with the US benchmark West Texas Intermediate for May delivery down 95 cents to $49.14 a barrel.