The leaders of Turkey, Russia, France and Germany gathered in Istanbul on Saturday to discuss the peace settlement in Syria. They are set to exchange views regarding the situation on the ground and developments around the Idlib buffer zone, agreed by Russian leader Vladimir Putin and his Turkish counterpart Recep Tayyip Erdogan in September. Under the deal, all weapons and hardline anti-government militants were to be cleared from the area by mid-October. The parties are also expected to discuss the use of chemical weapons in the Syrian conflict.