The UN special envoy to Syria is set to meet in Geneva this week with the foreign ministers of Turkey, Russia, and Iran — the partners in the Astana peace process — on the eve of the first meeting of Syria’s new Constitutional Committee.

Geir Pedersen told a press conference he would meet with Turkish Foreign Minister Mevlut Cavusoglu, his Russian counterpart Sergey Lavrov, and Iran’s Foreign Minister Mohammad Javad Zarif on Tuesday evening, before the committee’s inaugural meeting on Wednesday.

Read more: UN envoy to meet Turkish, Russian, Iranian foreign ministers