FILE PHOTO - U.N. envoy Staffan de Mistura (C) looks on before the start of talks on Syria in Vienna on January 25, 2018. REUTERS/Alex Halada/Pool

MOSCOW (Reuters) - United Nations Syria mediator Staffan de Mistura will head a new constitutional commission that will be set up at a peace conference in Russia this week, the Interfax news agency reported on Monday, citing official documents.

Russia is hosting a two-day Syrian Congress of National Dialogue in the Black Sea resort of Sochi on Monday and Tuesday which it hopes will launch talks on drafting a new constitution for Syria.