Iran nuclear talks may need new round - diplomats
Talks in Geneva on Iran's nuclear programme could need a new round, diplomats have said, as tough negotiations continued for a third day.
Iranian Foreign Minister Mohammad Javad Zarif told the BBC he was more cautious about a deal than two days ago, but was hopeful an agreement would still come.
A deal that was floated would require Iran to freeze expansion of its nuclear activity for limited sanctions relief.
Diplomatic sources said France wanted tougher terms for Iran.
The Geneva talks involve Iran and the P5+1: the US, Russia, Britain, France and China as permanent UN Security Council members, plus Germany.
Iranian President Hassan Rouhani had earlier urged the world powers not to miss an "exceptional opportunity" to seal an agreement.
UK Foreign Secretary William Hague had also urged negotiators to "seize the moment".
Delegates had been suggesting that "good progress" had been made but one Western diplomat told Associated Press they were now preparing an announcement of a new meeting in a few weeks' time.
The diplomat said France was holding out for tougher conditions.
French Foreign Minister Laurent Fabius told France Inter Radio his nation did not want to be part of a "sucker's deal" and referred to "several points that.. we're not satisfied with compared with the initial text".
One sticking point Mr Fabius mentioned was whether Iran should suspend operations at its Arak research reactor - a possible producer of weapons-grade plutonium.
Another was that Tehran was resisting demands to downgrade its stockpile of uranium enriched to 20%, he said.
The West suspects Iran's uranium enrichment programme is a step towards building nuclear weapons - a charge Iran strongly denies.
Iran's Tabnak news agency said Mr Fabius "has obstructed the reaching of a deal", but Mr Zarif was more discreet.
"I'm not going to tell you who is creating trouble," the Iranian foreign minister told the BBC's Middle East editor Jeremy Bowen.
"Some comments have been made publicly by Foreign Minister Fabius. Obviously he has some concerns. If we try to meet each other's concerns I think we can reach agreement."
Mr Zarif said he was more cautious about a deal than before, but that an agreement was coming.
He also said he had a message for US President Barack Obama - that a deal was attainable but that the window of opportunity would not be open indefinitely.
A press conference had been prepared for Saturday evening. However, the talks then continued and Mr Zarif has reportedly joined the world powers in a late-evening session.
The talks had begun on Thursday and expanded into unscheduled meetings between foreign ministers as expectations of a deal grew.
Although details of the suggested accord have not been disclosed, it is thought to offer Iran a gradual easing of sanctions in return for a freeze on expansion of nuclear activities.
This brought an angry response from Israel.
PM Benjamin Netanyahu said he "utterly rejected" such a deal with Iran, its long-time enemy, and that his country would not be obliged to abide by it.
Mr Obama later telephoned Mr Netanyahu to allay fears about any deal.
A White House statement said Mr Obama had repeated his commitment to stopping Tehran getting a nuclear weapon.
Since 2006 the UN Security Council has imposed a series of sanctions - including asset freezes and travel bans - on entities and people involved in Iran's nuclear programme.
Separate US and EU sanctions have targeted Iran's energy and banking sectors, crippling its oil-based economy.