Syria peace conference Geneva II begins in Switzerland

The Syrian government and the main opposition are attending the Geneva II summit along with international allies. UN Secretary General Ban Ki-moon told delegates they faced a "formidable challenge", but there was a chance to "make a new beginning".

However, correspondents say no major breakthroughs are expected soon. The key issue, on which neither side appears willing to budge, is the future of President Bashar al-Assad. Differences were also laid bare on the eve of the summit, in a report accusing Syria of mass torture and executions. Direct talks begin in Geneva on Friday. This would be the first time the Syrian government and the opposition have met face to face since the start of the conflict which, in addition to the dead, has left millions of Syrians displaced.

'Raising hope' Opening the summit - which will hear from some 40 or so foreign ministers - Mr Ban urged all parties to engage "seriously and constructively" in the talks.

"We know that it has been an extremely difficult path to reach this point. We have lost valuable time and many many lives," he said. "Let me not mince words - the challenges before you and before all of us are formidable. But your presence here raises hope."

He said the disaster was "all-encompassing" with a widespread disregard for humanitarian laws, but that Syrians remained "united in their love for their country". Russian Foreign Minister Sergei Lavrov said the talks "will not be simple, will not be quick", but that there was "a historic responsibility on the shoulders of all participants". He also repeated his insistence that Iran, whose invitation to the summit was revoked, should be involved. US Secretary of State John Kerry told the conference the uprising had begun as a peaceful process, but that "tragically the Assad regime answered peaceful demonstration after peaceful demonstration with ever increasing force". He said there was "no way possible" for there to be peace while Mr Assad remains in power.

In angry opening remarks, Syria's Foreign Minister Walid Muallem said some states attending the peace talks had encouraged terrorism and had "Syrian blood on their hands". Syria's neighbours had "lit fires" in the country " and "brought terrorists from all over the world", he said.

"Syria the independent state will do all that is necessary to defend itself."

'Patience and persistence' BBC diplomatic correspondent Bridget Kendall says the UN's main concern is to get an initial dialogue going on steps that will help beleaguered Syrians. She says there is talk of possible local truces and humanitarian access to besieged areas, but that even this may be a tall order, given the uncertainty that the Assad government will make real concessions and the lack of sway the opposition delegation has over the many rebel groups fighting in Syria.

International delegates to Geneva II have played down hopes of a breakthrough, saying the talks should be seen as the first step in a process.A senior US state department official told Agence France-Presse: "Everybody has to understand that this is the beginning of a process... And so there's going to be an absolute requirement for patience and for persistence."

German Foreign Minister Frank-Walter Steinmeier said: "We must have measured expectations. We will not see peace triumph during these discussions."

Mr Muallem earlier indicated that Damascus was "committed to working for the success of this conference so that it is the first step on the road to a dialogue between Syrians on Syrian soil". Earlier this week the UN withdraw its invitation to Iran to attend the talks, saying it had orally accepted the Geneva Communique, the plan for a transitional Syrian governing body agreed at a UN-backed meeting in 2012, only to later fail to put the commitment in writing.

Iran's President Hasan Rouhani said on Monday that the "lack of influential players in the meeting" meant he doubted its "success in fighting against terrorism... and its ability to resolve the Syria crisis".

"The Geneva 2 meeting has already failed without it even being started," state media quoted him as saying.

'Caesar' A report by three former war crimes prosecutors, released on Tuesday, alleged Syria had systematically tortured and executed about 11,000 detainees since the start of the uprising in March 2011. The report is based on the evidence of a defected military police photographer, referred to only as Caesar, who along with others reportedly smuggled about 55,000 digital images of the dead detainees out of Syria. The US and UN reacted with "horror" to the allegations.

A Syrian spokesman said the report had no credibility as it was commissioned by Qatar, which funds rebel groups.