The United Nations envoy for Syria announced on Wednesday he will step down at the end of November after more than four years in the key post as UN efforts to end the seven-year war show no sign of a breakthrough.
"I will myself be moving on as of the last week of November," Staffan de Mistura told the UN Security Council during a meeting on the crisis in Syria.
The Italian-Swedish diplomat, who is the UN's third Syria envoy in six years, said he was leaving for "purely personal reasons," citing the need to give his family "a little bit of attention" after a long stint in the demanding post.
De Mistura will be traveling to Damascus next week to push for the creation of a committee to agree on a post-war constitution for Syria that would pave the way to elections.
That plan has been under discussion since January when it was announced at a conference organized by Russia, a key Syrian ally, but it has since been bogged down in bickering over the committee's composition.
The Syria government is objecting to the UN-led effort to include civil society representatives, religious and tribal leaders, experts and women on the panel, the envoy said.
De Mistura said he hoped the committee will be up and running in November, before he leaves.
"I am not laying down the charge until the last hour of the last day of my mandate," he said.
More than 360,000 people have died in Syria's war, which began in March 2011 as an uprising against President Bashar al-Assad but has morphed into a complex conflict with myriad armed groups, some of whom are foreign-backed.
De Mistura was appointed UN envoy for Syria in July 2014 after veteran Algerian diplomat Lakhdar Brahimi resigned following the failure of peace talks in Geneva.
Brahimi spent two years in the position, stepping in after former UN chief Kofi Annan quit just six months into the role. Annan had described the Syria envoy's job as "mission impossible."
De Mistura's departure will complicate UN peace efforts at a time when Syrian forces have made significant territorial gains, prompting discussion about the terms of a political settlement to end the war.
Western powers maintain that there will be no reconstruction aid to Syria before a final settlement is reached.
During his tenure, De Mistura worked to keep UN-sponsored peace talks alive even as fighting on the ground, which has seen deadly chemical weapons attacks, killed off chances of a deal.
Last year, Russia, Iran and Turkey set up the Astana process to advance diplomatic efforts in Syria, a move that effectively sidelined the UN-led process that De Mistura was shepherding in Geneva.
Still, the 71-year-old diplomat, who is said to speak seven languages and favors pince-nez spectacles over conventional glasses, showed tenacity in the job.
While there were no breakthroughs in talks in Geneva, he insisted that incremental progress was being made.
Following his mission to Damascus, De Mistura will return to the Security Council in November for his final briefing.
Among the names being floated as a possible successor are the UN's Middle East peace coordinator Nickolay Mladenov and the UN envoy for Iraq Jan Kubic, according to UN diplomats.