The United Nations envoy on Syria signed off from his posting on Thursday ruing "a missed opportunity" to help end the country's long conflict at talks in the Kazakh capital of Astana. Staffan de Mistura announced his resignation last month and capped his term as peace envoy with two days of talks in the Kazakh capital, sponsored by power-brokers Russia and Iran – allies of the Syrian regime of Bashar al-Assad – and rebel-backer Turkey. A statement from his office noted he regretted that "no tangible progress in overcoming the 10-month stalemate on the composition of the constitutional committee" was made at the talks. The meeting in Astana was "a missed opportunity to accelerate the establishment of a credible, balanced and inclusive, Syrian-owned, Syrian-led, UN-facilitated constitutional committee," the statement said. The two-day negotiations that concluded Thursday, are the 11th in Astana since Moscow began a diplomatic push in early 2017 that effectively side-lined other talks on Syria led by the United Nations. Mr De Mistura’s Geneva track peace talks have effectively become mothballed and characterised by a failure to get all sides to sit down and agree on any tangible progress. The constitutional committee is viewed as a vital element in reaching a political settlement in the country. Speaking after the talks, Russia's Syria negotiator Aleksandr Lavrentyev said the committee was of utmosts importance". "I want to say that we are sufficiently close to our cherished goal," he added, without giving any date. The talks began Wednesday with a 10-week-old Idlib truce deal hanging in the balance after an alleged chemical attack in the government-held city of Aleppo on Saturday triggered retaliatory raids. The exact circumstances of the attack remain murky and bitterly disputed. <strong>______________</strong> <strong>Read more: </strong> <strong><a href="https://www.thenational.ae/world/mena/children-in-syria-s-war-being-killed-at-higher-rate-than-in-2013-1.797003">Children in Syria's war being killed at </a></strong><strong><a href="https://www.thenational.ae/world/mena/children-in-syria-s-war-being-killed-at-higher-rate-than-in-2013-1.797003">higher</a></strong><strong><a href="https://www.thenational.ae/world/mena/children-in-syria-s-war-being-killed-at-higher-rate-than-in-2013-1.797003"> rate than in 2013</a></strong> <strong><a href="https://www.thenational.ae/world/mena/crumbling-idlib-truce-tops-agenda-as-iran-turkey-and-russia-meet-in-astana-1.796954">Crumbling Idlib truce tops agenda as Iran, Turkey and Russia meet in Astana</a></strong> <strong>Opinion:<a href="https://www.thenational.ae/opinion/comment/us-and-turkey-could-influence-the-political-outcome-in-syria-if-they-put-their-differences-behind-them-1.796796"> US and Turkey could influence the political outcome in Syria – if they put can agree </a></strong> <strong>______________</strong> The Syrian government of Bashar Al Assad has blamed rebel fighters for the attack which the Syrian Observatory for Human Rights said hospitalised 94 people. The incident has strained an already fragile agreement reached in mid-September to fend off a fully-fledged assault on Idlib, which Syria's regime – backed by Russia and Iran – has said it is committed to re-taking. Speaking late on Wednesday, Russia's Lavrentyev said that "additional time" would be required to secure a buffer zone in the region of 3 million people after an uptick in fighting. The alleged chemical attack "must be dealt with very seriously," he said, calling for qualified international bodies to visit the city to assess the incident. Chemical weapons watchdog, the OPCW, has said it wants to investigate the incident and has asked the UN’s security team to check on the feasibility of deploying weapons inspectors to the site of the attack. On Sunday, Russia said its warplanes had carried out their first strikes in the zone since the deal was reached, in an apparent retaliation. The Astana talks have seen the United States, other Western countries and many Arab states kept at arm's length over Syria. A joint communique agreed by the three sponsors targeted Washington's continued military presence in the country. The guarantors "rejected all attempts to create new realities on the ground under the pretext of combating terrorism," it said. Earlier this week, Turkish President Recep Tayyip Erdogan accused the US of using the presence of ISIS in southern Syria as an excuse to keep forces stationed there. A recent push by the US to build military observation posts in Syria near the border with Turkey is a bid to prevent Ankara from launching an all-out military assault on positions held by Washington's Kurdish allies, according to experts. The Syrian Democratic Forces have repeatedly threatened to stop the fight against ISIS if Turkey continues to attack their positions. Ankara deems the SDF in the same light as the Kurdish guerrilla PKK movement that it designates as a terrorist group. Mr Lavrentyev also complained of the extended US presence during the talks in Astana. The United States has attended some previous Astana rounds as an observer but US Special Representative for Syria Engagement James Jeffrey last week ruled out Washington participating in the latest talks. The next set of Syria negotiations in Astana are scheduled for early February, according to the joint communique. Syria's grinding seven-year civil war has killed more than 360,000 people and displaced millions.