The UN envoy for Syria acknowledged Thursday that the latest round of peace talks for the war-ravaged country had failed, and blamed Damascus for the "golden opportunity missed".

Staffan de Mistura told reporters that "we did not have real negotiations, blaming in particular the government delegation's apparent lack of interest in discussing anything besides the fight against "terrorism".

His statement came at the end of the eighth round of indirect talks in Geneva between delegations representing Damascus and the opposition in Syria's brutal, nearly seven-year war.

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

The UN mediator, who has described himself as a "chronic optimist" and highlights incremental progress where others see stalemate, had voiced hope that the eighth round that opened on November 28, would mark the first "real negotiation".

- 'Disappointed' -

But as the round fizzled out Thursday, he acknowledged he was "disappointed."

"In spite of lots of efforts of my whole team, we did not have real negotiations," he told reporters.

While the opposition, which was united in one delegation for the first time, had seriously engaged in all subjects on the table, he said "the government engaged sadly only on one subject... terrorism."

Asked about the next steps, De Mistura said he would discuss the matter with UN chief Antonio Guterres and the UN Security Council, but that he hoped to organise a new round of talks next month.

"We are not going to give up," he said, stressing the need to find a political solution to the conflict that has killed more than 340,000 people since March 2011.

Talks this month have snagged on the issue of President Bashar al-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.

The Syrian government's top negotiator, Bashar al-Jaafari, slammed the opposition for "placing preconditions for the Geneva talks", and flatly rejected their call for direct negotiations until they dropped the demand.

"We don't have a partner," head of the opposition delegation Nasr al-Hariri complained to reporters.

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.

De Mistura said he planned to attend that meeting.

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.

De Mistura said he did not yet have enough information about the Sochi event to voice an opinion.

But he warned that "if the government is not willing to meet anyone who seems to have any type of different opinion and is not willing to discuss constitution and elections... I would be very concerned if I were those organising Sochi or any other initiatives."

- UN mediator 'undermined' -

Jaafari meanwhile harshly criticised De Mistura, insisting he had "undermined" his position as mediator when he publicly appealed to Moscow to push for new Syrian elections.

"His statement undermined his mandate as a facilitator of the talks, which will affect the entire Geneva process," Jaafari said.

In the interview with Swiss public broadcaster RTS late Wednesday, 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".

He called on Russian President Vladimir Putin to "convince the (Syrian) government that there's no time to lose" and to "push the government to accept" new elections, which such a vote should be monitored by the UN.

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.

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".

"Therefore nobody can influence us," he said.

Soure:AFP