The biggest push to date to end Syria's civil war descended into disarray on Tuesday after the opposition cancelled a meeting with the UN special envoy Staffan de Mistura in outrage at several hundred Russian air strikes since Monday.
Representatives of President Bashar al-Assad's government denounced the main opposition body the High Negotiations Committee (HNC) as disorganised and stuffed with "terrorists", while contradicting de Mistura that indirect peace talks had begun.
The latest Russian bombings since Moscow threw its military might behind Assad in late September allowed loyalist forces to edge towards breaking a long-running rebel siege on two government-held villages near Aleppo.
Russian Foreign Minister Sergei Lavrov said Wednesday that he saw no reason for the air strikes to stop, while slamming "capricious" elements in the HNC and the smuggling of arms from Turkey into Syria.
"Russian air strikes will not cease until we truly defeat the terrorist organisations ISIL and Jabhat al-Nusra," Russian agencies quoted Lavrov as saying in Oman.
He was referring to Islamic State, the extremist group which has overrun swathes of Syria and Iraq and which claims to be behind bombings and shootings worldwide such as in Paris, and to Al-Qaeda's Syrian branch.
But the opposition -- and Western countries -- say that Russia's barrage is almost entirely targeting other rebel groups, many of them backed by the West, Gulf states and Turkey.
"Russia is using the political process as a cover to impose its military solution on the ground," Salem al-Meslet from the HNC said.
- Zero confidence -
De Mistura's brief is to coax the warring parties in a conflict that has killed more than 260,000 people into six months of indirect talks in Switzerland under a roadmap agreed by outside powers in November.
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Since the conflict began in March 2011 as an uprising against Assad's rule, more than half of Syria's population have fled their homes -- many heading to Europe -- and for IS to expand.
The tangled conflict has dragged in a range of international players, from Iran, Turkey and the Gulf states to Western nations and Russia.
De Mistura said on Swiss television late Tuesday that if these talks fail, "all hope would be lost." He told the BBC said that "the level of confidence between the two parties is close to zero".
The HNC wants Assad to allow humanitarian access to besieged towns, to stop bombing civilians and to release thousands of prisoners -- some of them children -- languishing in regime jails.
Damascus says that the HNC has failed to present even a list of its negotiators and strongly objects to the inclusion within the Saudi-backed body of rebels that it and Moscow view as "terrorists".
One such figure is Mohammed Alloush, a leading member of Islamist rebel group the Army of Islam, in Geneva since Monday and nominally the HNC's chief negotiator, who said Wednesday he was "not optimistic".
"The problem is not with de Mistura. The problem is with the criminal regime that decimates children and with Russia which always tries to stand alongside criminals," he said, clutching a photo of a young boy he said was severely wounded by Russian air strikes.
- Hijab to the rescue? -
The HNC was on Wednesday in internal talks in a Geneva hotel -- barred to reporters since Tuesday -- to discuss its next steps, after a tense meeting the previous evening, an opposition source said.
Western diplomats expressed optimism that Riad Hijab, a former Syrian premier who defected in 2012, could help the HNC present a more united front and be a more acceptable interlocutor for all concerned.
"With Hijab here, the HNC can better demonstrate a unified position in representing the opposition," one said on condition of anonymity ahead of Hijab's expected arrival in Geneva late Wednesday.