The U.N. envoy for Syria, Staffan de Mistura, on Wednesday announced he will step down at the end of November after more than four years in the key post.

"I will myself be moving as of the last week of November," De Mistura told the U.N. Security Council during a meeting on the crisis in Syria.

The Italian-Swedish diplomat, who became the U.N.'s third Syria envoy in July 2014, said he was leaving for "purely personal reasons" and had discussed his plans to leave with U.N. Secretary-General Antonio Guterres.

"I am not laying down the charge until the last hour of the last day of my mandate," he said.

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.

Syria is resisting the U.N.-led effort to set up the constitutional committee that will be comprised of regime officials, opposition members and representatives of civil society.

De Mistura was appointed U.N. 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 U.N. chief Kofi Annan quit just six months into the role.

More than 360,000 people have died in the war in Syria, which began in March 2011 as an uprising against Bashar Assad but has since morphed into a complex war with myriad armed groups, some of which have foreign backing.