UN Special Envoy to the Secretary-General for Syria Staffan de Mistura arrives for a round of negotiation with Nasr al-Hariri (not pictured), Head of the Syrian Negotiation Commission, during the Intra Syria talks at the European headquarters of the United Nations in Geneva, Switzerland December 13, 2017. REUTERS/Salvatore Di Nolfi/Pool

GENEVA (Reuters) - U.N. Syria envoy Staffan de Mistura said Syria talks in the Kazakh capital Astana on Friday had agreed on a “working group” for the release of detainees, which he said was a commendable first step towards an arrangement between the warring sides.

He also said that Russia’s plan to convene a Syrian “congress of national dialogue” in Sochi next month should be assessed by its ability to contribute to and support the U.N.-led Geneva talks on ending the war in Syria.