The United Nations Special Envoy for Syria said on Sunday the government and opposition co-chairs of the Syrian Constitutional Committee had agreed to draft a new constitution.

The drafting committee, comprising 45 representatives of Syria’s government, opposition and civil society, has a mandate to draw up a new basic law leading to U.N.-supervised elections.

Special Envoy Geir Pedersen said its Syrian co-chairs, who he met together for the first time ahead of week-long talks, had agreed to "prepare and start drafting constitutional reform."

The talks, the sixth round in two years and the first since January for the drafting committee, will discuss "clear principles", he told reporters in Geneva, without elaborating.

Hadi Al-Bahra, the co-chair of the Syrian Constitutional Committee, said its opposition delegation was seeking reforms including equal rights for all Syrian citizens.

"Because we don't have separation of power in the current constitution, it created an imbalance which was utilised in the wrong ways," he told a separate news briefing on Sunday night.

Each side would put forward proposed texts on issues including sovereignty and rule of law, he said.

Syrian government delegates to the talks did not speak to the media.

Syria's decade-old war spiralled out of an uprising against President Bashar al-Assad's rule.

After support from ally Russia, Assad has recovered most of Syria, but significant areas remain outside his control: Turkish forces are deployed in much of the north and northwest and U.S. forces are stationed in the Kurdish-controlled east and northeast.

In January Pedersen, a veteran Norwegian diplomat, said Assad's representatives had rejected proposals by the Syrian opposition as well as the envoy’s own ideas for moving the constitutional process forward.

"Since then... I have been ...trying to be able to establish a consensus on how we are going to move forward. And I am very pleased to say that we have reached such a consensus," he said on Sunday.

Western diplomats say Russia prodded Damascus in recent weeks to show flexibility in the talks, and Pedersen has made two trips to Moscow in recent months.

"The Syrian Constitutional Committee is an important contribution to the political process but the committee in itself will not be able to solve the political crisis," he said.