A general view of the Kazakh capital Astana. Picture used for illustrative purposes only. File/AFP
The four countries have been discussing Syria's future after 12 years of civil war, during which Russia and Iran supported President Bashar al-Assad while NATO member Turkey backed political and armed opposition to him.
Foreign ministers from the four countries met in Moscow on May 10, and Russia said at the time that deputy ministers would be tasked with preparing a roadmap to advance Syria-Turkey ties.
Reuters