GENEVA (Reuters) - The U.N. diplomat trying to convene talks to end the war in Syria said he first hopes to get an understanding between Russia and the United States, which will each then form the core of one or more "contact groups" of interested countries supporting the talks.

U.N. envoy Staffan de Mistura told a news conference that he would hold talks in Russia on Tuesday and then in Washington, and said the escalating violence made it more urgent to hold dialogue between Syrian government and opposition groups.

(Reporting by Stephanie Nebehay, editing by Tom Miles)