UN Special Envoy for Syria Staffan de Mistura, who will leave his post at the end of November, will also arrive in Istanbul on Saturday to brief the participants in the summit on the recent developments. De Mistura said earlier that he wants to remind the four leaders that after localizing the problem in Idlib, an international consensus is necessary to support UN actions on establishing a constitutional committee.
The Turkish president was the first to come forward with a proposal to hold a quadrilateral summit. Russia supported this initiative. In mid-September, aides on international issues to the leaders of Russia, Germany, Turkey and France met to discuss the substantive part of the summit.