Iran and world powers scored a major breakthrough with a framework deal aimed at stopping Tehran getting nuclear weapons, but major work is needed to finalise the potentially historic accord, analysts said yesterday.

In addition, those alarmed by what was agreed, not least US President Barack Obama's Republican opponents, may yet scupper the entire process before the June 30 deadline to sign on the dotted line.

"This accomplishment is not final. It is as fragile as the forces against it are formidable," Ali Vaez from the International Crisis Group told AFP.

"A lot of thorny issues will have to be resolved in the next three months."

Iran and six major powers late on Thursday agreed after 18 months of talks, culminating in a gruelling marathon of sleepless nights in a Swiss hotel, the main parameters of what the final deal will look like.

According to the US, Iran has promised to slash its uranium enrichment capacity - which makes nuclear fuel but also the core of a bomb - by two-thirds and reduce its enriched uranium stock by 98 percent.

The framework agreement was however very light on detail on when

exactly all this will happen once the final comprehensive deal is agreed on June 30.

Iranians, who celebrated on the streets in the early hours of Friday when the news from Lausanne came through, want to see sanctions lifted quickly to boost the economy and attract foreign investment.

But the sanctions will not all be lifted in one fell swoop on July 1.

Instead they will be tied to Iran first

carrying out what it has undertaken to do, something to be verified by the UN atomic watchdog, the International Atomic Energy Agency.

In addition, there will be the possibility for a "snap" back of the sanctions if Iran violates the deal.

The task of the next three months therefore will be to hammer out in minute detail a timetable for which sanctions are eased when, and what

Iranian actions they will be dependent upon.

One potential snag is that in addition to slashing its capacities, Iran will also have to clear up allegations that before 2003, and possibly since, it did research into makinga nuclearweapon.

Other potential problem areas are the language that goes into a mooted new UN Security Council resolution to replace the six others that will be lifted, and the mechanism fordeterminingviolations.

“The agreement also does not spell out the specific timeline for Iran's compliance with the IAEA investigation," Arms Control Association expert Kelsey Davenport told AFP.

According to Vaez, the most important “wildcard" is US lawmakers who believe the concessions made constitute a humiliating climbdown that will not do enough to stop Iran getting the bomb.

Republican pressure could make it hard for Obama to lift US sanctions while mooted new legislation they want to bring could impose further measures and force the president to get lawmakers' approval for the deal.

"The US Senate should avoid taking any steps to undermine this frame-work,' Tom Collina from Ploughshares Fund said. "This could kill the deal before it is finished."