US Secretary of State John Kerry (L) meets with Iran's Foreign Minister Javad Zarif (R) over Tehran's nuclear program in Lausanne, Switzerland, on March 20, 2015
Lausanne (AFP) - Marathon talks aimed at putting an Iranian nuclear bomb out of reach broke up Friday without a breakthrough, with negotiators opting to try again next week to narrow still major differences.
That will leave Iran and six major powers just one week to meet a March 31 deadline for agreeing the outlines of a deal that they hope will end a 12-year standoff.
"Right now more consultation and coordination is needed," Iranian Deputy Foreign Minister Abbas Araghchi said, adding that the next round would begin on Wednesday, although where the talks would be held was unclear.
After five days of "intensive discussions" US Secretary of State John Kerry will leave Switzerland on Saturday for talks in London with his British, French and German counterparts, the State Department said.
"(Given) where we are in the negotiations, it's an important time for high-level consultations with our partners in these talks," spokeswoman Marie Harf in Lausanne.
On Friday Kerry spoke by phone with the foreign ministers of Russia and China, the other two powers involved in talks that first began in earnest after the 2013 election of Iranian President Hasan Rouhani.
French President Francois Hollande, who earlier Friday discussed the Iran talks with German and British counterparts Angela Merkel and David Cameron, said he would talk with US President Barack Obama later Friday.
- Obama address -
Overnight Obama appealed in a Nowruz (Persian New Year) address to the Iranian "people and leaders" to seize an "historic" opportunity and begin a "brighter future".
"I believe that our nations have an historic opportunity to resolve this issue peacefully -- an opportunity we should not miss," Obama said.
In an apparent response, Iranian Foreign Minister Mohammad Javad Zarif, who has been locked in talks with Kerry in Lausanne all week, said it was the other side that had to budge.
"Iranians have already made their choice: engage with dignity. It's high time for the US and its allies to chose: pressure or agreement," Zarif wrote in a message posted on his official Twitter account.
"Nowruz is the beginning of spring, and in Farsi, it means 'new day'. I hope this new day will be a new day for the entire world –- a new era of greater understanding and peace," Zarif told Kerry.
- Complex deal -
The highly complex mooted agreement, due to be finalised by July, is aimed at convincing the world that Iran will not build nuclear weapons under the guise of its civilian programme.
It would likely involve Iran reducing in scope its nuclear activities, allowing ultra-tight inspections, exporting nuclear material and limiting development of new nuclear machinery.
In exchange, Iran -- which denies wanting nuclear weapons -- would get staggered relief from the mountain of painful sanctions that have strangled its oil exports and hammered its economy.
Obama's Republican opponents and Israel's re-elected Prime Minister Benjamin Netanyahu, whose country is assumed to possess nuclear weapons itself, fear the deal will not do enough to stop Iran getting the bomb.
Negotiators missed two deadlines last July and November for a deal but the pressures in Washington -- where Republicans are teeing up new sanctions legislation -- all but rule out a new extension, experts say.
- Gaps remain -
Both Kerry and Zarif on Thursday spoke of "progress" but both sides have said that there remain considerable gaps.
"I think we are pretty far from a deal," a European negotiator involved said on Thursday. "The Iranians go back, go forward, it changes every day."
Together with the future size of Iran's nuclear programme, a key sticking point is Iran's demand to have UN Security Council resolutions lifted "on day one" of the accord, the European said.
"They (the Iranians) say it is a deal breaker... But there is no way we will give way on this," the diplomat said on condition of anonymity.
But some of the US and EU sanctions that have choked Iran's oil exports and cut its banks off from the global financial system could be suspended within six months to a year, he said.