The UN envoy for Syria on Monday signaled that he was ready to abandon efforts to set up a committee on drafting a post-war constitution if no deal is reached by the end of December.
The planned constitutional committee agreed at a Russia-hosted conference in January has run into objections from the Syrian government over allowing religious leaders, representatives from women's groups and independent experts to take part.
The centerpiece of UN peace efforts in Syria, the committee would be tasked with negotiating a new post-war constitution that would pave the way to elections aimed at turning the page on seven years of devastating war.
"We are in the last days of the attempts to implement the constitutional committee," envoy Staffan de Mistura told a Security Council meeting on the Syria crisis.
"We may have to conclude that (it) may not be possible to form a constitutional committee, credible and inclusive, at this stage," said the envoy, speaking by videoconference from Geneva.
"In such an unfortunate case, I will certainly be ready to explain to the council why," he warned.
De Mistura, an Italian-Swedish diplomat who has been the UN's peace envoy since July 2014, was due to step down at the end of November, but he agreed to stay on for an extra month to lead a final push.
The United Nations is still hoping to send invitations to committee members by mid-December and convene a first meeting before December 31, said the envoy.
The leaders of Russia, Turkey, Germany, and France have called for the committee to be formed by the end of the year.
Norwegian diplomat Geir Pedersen has been appointed to become the fourth UN envoy for Syria since the war began in 2011.
Russia and Iran, which are providing crucial military support for Syrian President Bashar al-Assad, and Turkey, which supports some armed groups, will meet next week in the Kazakh capital, Astana.
More than 360,000 people have been killed in the war, which began in March 2011 as an uprising against Assad but has morphed into a complex conflict with myriad armed groups, many of whom are foreign-backed.
