'Good progress' in Iran deal talks
Efforts to secure an interim deal with Iran over its nuclear programme have made "good progress", Foreign Secretary William Hague said as talks continued in Geneva.
But he stressed that there remained "important issues to be resolved" in the negotiations, which are expected to be joined by both Russia and China later, fuelling optimism about an agreement.
"We will try to maintain the momentum," Mr Hague wrote on Twitter from the Swiss city where he has joined the high-level diplomatic push.
US Secretary of State John Kerry sat down with his Iranian counterpart Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton for five hours yesterday.
Washington and Tehran both suggested progress had been made but that there was more work to do, with Mr Kerry speaking of "important gaps" still to be closed.
French and German foreign ministers are also at the meeting which is seeking a deal to ease sanctions in return for guarantees Iran's nuclear ambitions are civil not military.
Russian foreign minister Sergey Lavrov and a Chinese deputy foreign minister are expected to join them.
The attempted deal - reported to allow Iran to continue enriching uranium so long as it is only to the level required for nuclear power and not weapons - has been criticised by Israel.
Prime minister Benjamin Netanyahu said any such agreement was a "bad deal" as it would not stop Iran resuming military-related activities.
Any breakthrough would be the first after nearly 10 years of efforts and potentially pave the way towards a more comprehensive agreement to prevent Tehran producing nuclear arms.
Iran has always denied it has any ambition to do so, insisting its nuclear programme is entirely for the purpose of energy, medical treatments and research.
Prime Minister David Cameron and French president Francois Hollande discussed the situation in a phone call and agreed there was a " real opportunity to make significant progress", Downing Street said.
Mr Hague decided to attend in the hope the presence of the E3+3 negotiating group - the UK, France, Germany, Russia, China and the US - might help the process move towards a successful conclusion.
"It is for Iran to be able to convince the international community that it is able to address the deep concerns that the international community has," Downing Street said.
"We have always said we wanted to find a diplomatic solution. That is why we have had these E3+3 talks."
Among sanctions it is believed could be lifted are a freeze on up to £31 billion in overseas accounts and restrictions on petrochemicals, gold and other precious metals with t hose on oil exports and the financial sector expected to remain in place pending more detailed negotiations on a full deal.
Mr Hague said the atmosphere at the talks was "completely different" from a few months ago but stressed that there was no certainty of any agreement being reached by the end of the day.
"There are still important issues to resolve. We are going to have to give a lot of time and attention to those issues during the course of today and there is no fixed time for us to reach a conclusion," he told reporters.
"It's certainly not possible to say that we can be sure there will be a deal at the end of today. And if there isn't of course then we must continue to apply ourselves in the coming weeks, building on the progress that has been made.
"The atmosphere at these negotiations...is completely different from the atmosphere of a few months ago."
Mr Cameron telephoned Mr Netanyahu to discuss the latest developments in the talks, Downing Street said - as optimism waned that a deal was imminent.
No details were given of the contents of their conversation, which lasted around 10 minutes.
US President Barack Obama has also called the Israeli leader, assuring him of America's continued commitment to preventing Iran from obtaining a nuclear weapon.
It appears increasingly likely that the talks will end without agreement and a further round will be scheduled, with the French said to be holding out for tougher conditions on Tehran.
Foreign Minister Laurent Fabius told France-Inter radio there were "several points that... we're not satisfied with compared to the initial text" and that he would not be part of a "con game".
Mr Zarif said " differences" remained and that negotiations would resume in a week to 10 days if no agreement was found by the end of the day.
Iran's IRNA news agency quoted President Hassan Rouhani as saying the leaders should take the " exceptional opportunity that the Iranian nation has provided to the West and the international community so that we achieve a positive result in a reasonable time".