Syria says Russia congress 'cornerstone' of solution

A Syria peace congress hosted this week by ally Russia is the "cornerstone" of any solution to the country's nearly seven-year conflict, a government source said on Thursday.Tuesday's congress in the Black Sea resort of Sochi, snubbed by Syria's main opposition and the Kurds, agreed on the creation of a commission to discuss the country's post-war constitution.UN Syria envoy Staffan de Mistura, who attended the meeting, said the United Nations would lead efforts to form the commission.