Iran and world powers have reached tentative agreement on parts of a deal sharply curtailing Tehran's nuclear programme, Western diplomats said on Sunday (Mar 29) while cautioning that the deal is by no means done.
As negotiators raced against the clock in a rainy Switzerland, in Israel Prime Minister Benjamin Netanyahu launched a blistering attack on the "dangerous" accord that may be emerging.
One Western diplomat said Iran had "more or less" agreed to slash the number of its centrifuge machines by more than two-thirds and to ship abroad most of its stockpile of nuclear material.
A senior Iranian negotiator denied any such thing, saying any such claims were aimed at "disturbing" the talks. "No deal has been reached, and the remaining issues have to be resolved," the Iranian official said.
But at the same time Iranian officials have expressed guarded optimism that after 18 months of tortuous negotiations and two missed deadlines, a breakthrough might be in sight for a deal ending 12 years of tensions.
"If we manage to resolve all the remaining issues today or in the next two to three days, then we can begin to draw up a text. But for the moment we are still in discussions," a source close to the Iranian delegation said on Sunday.
In Lausanne, US Secretary of State John Kerry cancelled plans to leave for an event in Boston on Monday in order to keep negotiating, the State Department said.
"It's going all right. We're working," Kerry said on Sunday during a break from talks with Iranian Foreign Minister Mohammad Javad Zarif at a luxury hotel in the Swiss town.
His French and German counterparts, Laurent Fabius and Frank-Walter Steinmeier, also scrapped plans to go to Kazakhstan, diplomats said. Steinmeier said Saturday talks were in the "endgame".
Chinese Foreign Minister Wang Yi arrived on Sunday morning. Russian and British top diplomats Sergei Lavrov and Philip Hammond were expected later, completing the line-up of foreign ministers.
AIM OF THE GAME
The aim is to agree broad outlines for an accord by Tuesday's midnight deadline, and then flesh out a series of complex annexes containing all the technical details by Jun 30. The mooted deal would see Iran scale down its nuclear programme and allow unprecedented inspections of its remaining activities.
The hope is to prolong the theoretical "breakout" time that Iran would need to produce enough fissile material to build a nuclear bomb to at least a year from the current estimate of several months.
This would require a combination of slashing the number of centrifuges, converting existing nuclear plants such as the underground Fordo facility, exporting its stocks of enriched uranium and limiting the development of newer, faster equipment.
The latter is thought to be a particularly thorny issue, as is the issue of sanctions. Iran is insisting that in exchange global powers must lift sanctions that have choked its economy by strangling its oil exports and banks.
The issue of UN sanctions is proving particularly thorny, diplomats said, with global powers insisting the sanctions should be eased only gradually to ensure that they can be "snapped" back into place if Iran violates the deal.
"Ultimately, it's time for the Iranians to send a clear signal to the international community about whether or not they're willing to make the serious commitments required," White House spokesman Josh Earnest told ABC television on Sunday.
But for Israel and US President Barack Obama's Republican opponents, the agreement will not go far enough to stop Iran one day getting the bomb.
Kerry is under pressure to return from Lausanne with something concrete to head off a push by Republican lawmakers to introduce yet more sanctions, potentially torpedoing the whole negotiating process.
"The dangerous accord which is being negotiated in Lausanne confirms our concerns and even worse," Netanyahu said in remarks broadcast on public radio.
He said the "Iran-Lausanne-Yemen axis" was "dangerous for all of humanity" and that combined with Tehran's regional influence, a nuclear deal could allow Iran to "conquer" the Middle East.
"I just don't understand why we would sign an agreement with a group of people who in my opinion have no intention of keeping their word," House Speaker John Boehner, due to travel to Israel this week, told CNN.
Russia has also warned that US-supported airstrikes by Iran's foe Saudi Arabia on Iran-backed rebels in Yemen - hence Netanyahu's comment - were "having an impact" on the negotiations.