Russia asks Assad to stop bombing as talks begin

"Russia announced to everyone that they have formally asked the Syrian government to silence their own skies during the talks," de Mistura told reporters in Geneva at a meeting on the eve of new UN-backed talks.

Russia began a bombing campaign in Syria in September 2015 in support of President Bashar al-Assad, with its special forces also operating on the ground in the country.

The veteran diplomat, however, signalled that limited progress was likely and "momentum" towards a deal was probably the most that could be hoped for when delegations for Assad and the opposition resume talks on Thursday.

"Am I expecting a breakthrough? No, I am not expecting a breakthrough," de Mistura said, adding that he hoped this round could lead to further talks on a political solution.

The ground – both in territory and diplomatically – has shifted since the last round of talks broke up in April 2016, and the rebels are in a significantly weaker position after losing the rebel bastion of eastern Aleppo.

Rival negotiators arrived in Geneva on Wednesday for talks aimed at ending Syria's six-year conflict with persistent violence and deadlock over the country's political future dampening hopes of a breakthrough.

An adviser for High Negotiations Committee told The New Arab: "There will be no possibility of a political solution unless there is a genuine transition from an authoritarian autocracy to a plural democracy.

"There must be a radical change within the structure of the regime, which has proven unable to initiate satisfactory reforms for Syrians, " the source, who spoke anonymously, added.

He added that the HNC was the only representative of the Syrian rebels and attempts by "the Cairo and Moscow groups to create other representative bodies will prove useless" referring to rival opposition groupings.

HNC chief negotiator Mohammad Sabra told The New Arab that the UN Security Council's resolutions, as well as international legitimacy, clearly supported the demands of the Syrians and their rights.

The latest truce on December 30 was brokered by opposition supporter Turkey and regime-backer Russia ahead of separate negotiations that also involved Iran in Kazakhstan.

The deal has reduced violence but fighting flared again this week including a government bombing campaign on rebel territory around Damascus.