The UN mediator at Syria peace talks in Geneva has "undermined" his position by appealing to Moscow to convince Damascus to hold new elections, the Syrian government's top negotiator said Thursday.

Bashar al-Jaafari harshly criticised UN envoy Staffan de Mistura for comments made to Swiss television Wednesday calling on Russian President Vladimir Putin to "have the courage" to convince his Syrian counterpart to allow new polls.

"His statement undermined his mandate as a facilitator of the talks, which will affect the entire Geneva process," he told reporters as the eighth round of negotiations concluded with no sign of progress.

Seven previous rounds of talks mediated by de Mistura have also gone nowhere -- and rival sides have not yet met face-to-face.

Speaking to Swiss public broadcaster RTS, the UN mediator said that Damascus's apparent military victory in Syria's nearly seven year war was not enough for President Bashar al-Assad and that new elections were needed for him to "win the peace".

De Mistura said Putin "had to convince the (Syrian) government that there's no time to lose". 

"We can talk about having won the territorial war, which is temporary, but the peace also needs to be won and for that there needs to be the courage to push the government to accept" new elections, he said, stressing that such a vote should be monitored by the UN.  

Jaafari emphasised that while Syria's government may have "allies, friends and people who fight with us on the ground," it enjoys "the highest possible degree of sovereignty".

 

- 'Nobody can influence us' -

 

"Therefore nobody can influence us," he said, insisting that "what the envoy mistakenly said as a linguistic slip ... does not reflect the relationship between us and Moscow."

Russia intervened in Syria's devastating conflict in 2015, providing aerial and ground support for government forces, ostensibly to combat advances by what Moscow and Damascus term "terrorist" groups.

On Tuesday, the first Russian troops began returning home after Putin ordered a pullout, saying their mission had been largely completed.

Talks this month have snagged on the issue of Assad's future, with the opposition delegation defying calls to give up its demand that the president must go as part of any peace deal.

Jaafari slammed the opposition, united in one delegation for the first time, for "placing preconditions for the Geneva talks" after a communique was published in Riyadh last month insisting on Assad's removal.

And he said Saudi Arabia and the western countries who support the opposition had "torpedoed" the talks and never wanted "Geneva to succeed in the first place".

A parallel process organised by Moscow and including fellow government ally Iran and rebel backer Turkey, is set to resume next week in Astana, Kazakhstan.

The Kremlin also hopes to convene a political congress in the Black Sea resort of Sochi which would bring together regime officials and the opposition to reinvigorate a hobbled peace process.

The opposition and Western diplomats are concerned that the Sochi meeting might be part of an effort by Moscow to circumvent the UN talks and impose a solution favourable to Assad. 

More than 340,000 people have been killed since the conflict broke out in March 2011 when protests against Assad's rule sparked a brutal crackdown.