Speaking to journalists in New York on Monday, Mr Guterres said that the Committee – which is to represent all sides in the conflict – would meet in Geneva “in the coming weeks”, in line with past Security Council resolutions.

“I strongly believe that the launch of the Syrian-owned and Syrian-led Constitutional Committee can and must be the beginning of the political path out of the tragedy towards a solution, in line with resolution 2254, that meets the legitimate aspirations of all Syrians and is based on a strong commitment to the country’s sovereignty, independence, unity and territorial integrity,” he said.

Consultations between the Syrian Government and the opposition Syrian Negotiations Commission are to be facilitated by the UN in Geneva and led by the UN Special Envoy for Syria, Geir Pedersen.

Earlier on Monday, Mr  Pedersen announced that he had held a “very positive meeting” on “remaining issues” related to the formation of the Constitutional Committee with Syrian Deputy Prime Minister and Foreign Minister Walid Muallem.

He also held similarly positive meetings on Monday with the leader of the Syrian Negotiations Commission, Nasser Hariri, he said in a statement.

While acknowledging his appreciation for the engagement of Russia, Turkey and Iran in backing the agreement on a Constitutional Committee, Mr. Guterres noted that the panel’s work “must be accompanied by concrete actions to build trust and confidence”.

The UN chief’s comments come amid repeated warnings by senior UN aid officials of a looming humanitarian catastrophe in Idlib -  the last opposition-held zone in Syria.

In a recent update on the situation in the north-west enclave – four months into the latest escalation of hostilities there -  the UN Office for the Coordination of Humanitarian Affairs (OCHA) said that that the situation for people in northwest Syria continues to deteriorate.

Hundreds of civilians have been “killed or injured due to airstrikes and shelling since 1 May”, the agency said.

To escape the violence between Government forces and non-State armed groups, some 630,000 people have fled their homes and to reach essential services that they need to survive, the OCHA update continued, with most moving to densely populated areas close to the Turkish border where aid capacity is overstretched.