Russia, Turkey and Iran failed to make any tangible progress in setting up a Syrian constitutional committee at a meeting in the Kazakh capital Astana, the office of U.N. Syria envoy Staffan de Mistura said in a statement on Thursday.
"Special Envoy de Mistura deeply regrets ... there was no tangible progress in overcoming the ten-month stalemate on the composition of the constitutional committee," it said.
"This was the last occasion of an Astana meeting in 2018 and has, sadly for the Syrian people, been a missed opportunity to accelerate the establishment of a credible, balanced and inclusive, Syrian-owned, Syrian-led, UN-facilitated constitutional committee."
The three countries said in a joint statement issued after the talks that they would "intensify" consultations to establish the committee as soon as possible.
"The Russian side views the outcome of the conference as positive," Russia's Syria envoy Alexander Lavrentiev told a briefing in Astana after the talks.
Moscow, Tehran and Ankara also said in the joint statement they were concerned with ceasefire violations in the Idlib demilitarized zone in northwest Syria and "would step up their efforts to ensure observance", but stressed the need to continue to "fight against terrorism" there.
This would include enhancing the work of the Iranian-Russian-Turkish coordination centre, the statement issued on the last day of the two-day meeting said.
Damascus-ally Russia and Turkey, which backs Syrian rebels, in September agreed to create a de-militarization buffer zone around the insurgent-held Idlib enclave.
But shelling exchanges have been common since then and the first air strikes since the deal hit the area on Sunday, after Russia and Damascus accused Idlib-based rebels of using chemical weapons to attack the government-held city of Aleppo on Saturday, a charge they deny.