Russian President Vladimir Putin is set to host his Iranian and Turkish counterparts in Sochi on Thursday to discuss how to resolve the conflict in Syria as Daesh makes a last stand in the east of the country and Washington prepares to withdraw troops.

A flurry of diplomatic efforts this week are focusing on the eight-year conflict in which some 500,000 people have died.

The international anti-Daesh coalition is set to meet on the sidelines of the Munich Security Conference while US Secretary of State Mike Pompeo will attend a conference on the Middle East in Warsaw.

Russian Foreign Minister Sergei Lavrov said on Wednesday the leaders would discuss forming a special committee tasked with drawing up a new post-war constitution for Syria.

At their meeting in the Black Sea resort of Sochi, Putin and Iran's President Hassan Rouhani – who back Syrian regime leader Bashar al Assad – and Turkey's opposition-backing President Recep Tayyip Erdogan are set to discuss ways to advance intra-Syrian dialogue.

Russia has been a key player in the conflict since launching a military intervention in 2015 in support of Assad's regime, which now controls almost two-thirds of the country.