The Syrian regime rejected on Friday the lineup of a committee proposed by the United Nations to draw up a new constitution. Outgoing UN special envoy to Syria Staffan de Mistura told the Security Council that Syrian Foreign Minister Walid Muallem had rejected the draft composition. The committee is seen as key to ending the country’s civil war. The special envoy has been working since January on the make-up of a committee to thrash out a new constitution and which would have 150 members: 50 proposed by the Syrian regime, 50 by the opposition and 50 by the UN, to include representatives of civil society and technical experts. De Mistura said it was the last list of UN-proposed names that the Syrians had rejected during talks on Wednesday. "Walid Muallem didnt accept a role for the UN in identifying or selecting a third list," the Italian-Swedish diplomat said. "Rather, Mr. Muallem indicated that the government of Syria and Russia had agreed recently that the three Astana guarantors (Russia, Iran and Turkey) and the Syrian regime would in consultations among them prepare a proposal as regards the third list," he said. He said Muallem asked that he withdraw the UN list he had submitted, something he said was only possible "if there was an agreement on a new credible, balanced and inclusive list" that complied with UN resolutions and commitments made in January talks in the Russian resort town of Sochi. Western powers, led by the United States, Britain and France, condemned Syrias obstruction of the committee, which they said needed to be put together without delay. The conflict, which began with anti-regime street protests in 2011, has claimed more than 360,000 lives. On the ground, regime artillery fire Friday killed seven civilians in Idlib, in the highest death toll since a deal last month to prevent a regime assault on the province, a monitor said. Three children were among those killed in the countrys last major opposition bastion in the northwest of the country, the Britain-based Syrian Observatory for Human Rights said. Regime ally Russia and rebel backer Turkey agreed on September 17 to set up a buffer zone around the Idlib region, which includes the province of the same name and parts of adjacent provinces. In the neighboring province of Aleppo, regime fighters and opposition factions exchanged gunfire on the western outskirts of the provincial capital, the Observatory said.