U.S. Secretary of State John Kerry (C), Russian Foreign Minister Sergei Lavrov (L), and United Nations Special Envoy for Syria Staffan de Mistura attend the International Syria Support Group meeting at the Palace Hotel in Manhattan, New York, U.S., September 22, 2016. REUTERS/Darren Ornitz

NEW YORK (Reuters) - U.N. Syria mediator Staffan de Mistura described a meeting of the International Syria Support Group on Thursday as “long, painful and disappointing,” adding that he wants to believe that Russia and the United States are serious about brokering peace.

Following the meeting on the sidelines of the annual U.N. gathering of world leaders, de Mistura also said it was wrong to declare a cessation of hostilities in Syria dead.