(L to R) Russian Foreign Minister Sergei Lavrov, U.S. Secretary of State John Kerry and UN Special envoy for Syria Staffan de Mistura attend a meeting of the International Syria Support Group on Syria in Vienna, Austria, May 17, 2016. (Xinhua/Qian Yi)

Photo taken on May 17, 2016 shows the meeting of the International Syria Support Group on Syria in Vienna, Austria. (Xinhua/Qian Yi)

Xie Xiaoyan (L front), China's envoy to the International Syria Support Group (ISSG), attends the meeting in Vienna, Austria, May 17, 2016. (Xinhua/Qian Yi)

Russian Foreign Minister Sergei Lavrov (L), U.S. Secretary of State John Kerry (C) and United Nations special envoy on Syria Staffan de Mistura attend a press conference after a meeting of the International Syria Support Group on Syria in Vienna, Austria, on May 17, 2016. (Xinhua/Qian Yi)