LAUSANNE (AFP) - Iran and global powers sealed a deal on Thursday on plans to curb Teheran's chances for getting a nuclear bomb, laying the ground for a new relationship between the Islamic republic and the West.

Though the agreement was hailed as a major breakthrough in a 12-year standoff between Iran, Europe and the United States, world leaders couched their reactions, underlining a lack of trust in Teheran and scepticism in some quarters that the hard-fought deal could stay standing.

Here are some of the quotes from the main protagonists in the talks between Iran and the P5+1, made up of the United States, Britain, France, China, Russia and Germany:

Obama cheers historic deal, warns Iran

"I am convinced that if this framework leads to a final comprehensive deal, it will make our country, our allies and our world safer," said US President Barack Obama.

While he cheered the "historic understanding" and told sceptical hardliners the diplomatic solution to the standoff was the "best option by far", he admitted there was a risk Teheran would not hold up its end of the bargain.

But "if Iran cheats, the world will know it," he said.

Zarif hails thawed Iran-West relations

Iranian Foreign Minister Mohammad Javad Zarif hailed a thawing in US-Iran relations, saying the deal brought to an end a negative "cycle that was not in the interest of anybody" and showed "true dialogue and engagement with dignity" meant "we can resolve problems, open new horizons and move forward."

Hammond: 'More than we hoped for'

"This is well beyond what many of us thought possible even 18 months ago", British Foreign Secretary Philip Hammond said, adding that while "we will continue to have our differences on many other issues with Iran," the deal will crucially "avoid a nuclear arms race in the region."

Russia defends Iran's rights

"This deal contains the principal put forward by Russian President Vladimir Putin, which is Iran's unconditional right to a peaceful nuclear programme," the Russian foreign ministry said.

Kerry: World safer

US Secretary of State John Kerry said diplomacy had paid off, insisting that "simply demanding that Iran capitulate makes a nice sound bite, but it's not a policy."

Admitting the United States "remains deeply concerned about Iran's destabilising the region", he said the test now would be "whether or not it will leave the world safer or more securer than it would be without this agreement."

Merkel: Closest deal in history

German Chancellor Angela Merkel acknowledged the sweat, blood and tears that had gone into clinching the deal, saying the international community had never "been so close to an agreement preventing Iran from having nuclear weapons".

Ban Ki-moon sees boost in Mideast cooperation

UN Secretary-General Ban Ki-moon said it will pave the way to bolstering "peace and stability" in the Middle East and allow cooperation on the "many serious challenges (countries) face" in the region.

France wary

While French Foreign Minister Laurent Fabius embraced the accord as "unquestionably positive" in parts, President Francois Hollande's office warned "sanctions that are lifted can be re-imposed if the deal is not applied," and called for a "verifiable" final agreement on Iran's progress.

Israel: 'Historic mistake'

Israel's Prime Minister Benjamin Netanyahu, who had been violently urging the West not to sup with Iran, even with a long spoon, did not immediately react to the announcement.

An Israeli government source, however, slammed the accord as a "historic mistake."

Israel, widely believed to have the bomb itself, has said a bad deal would endanger the country.