The United States, Russia, Iran and 14 other powers called on Friday for a nationwide truce in Syria's four-year civil war, a renewal of stalled U.N.-brokered talks between the government and opposition and fresh elections. In a joint statement after talks in Vienna, the participants said "substantial differences remain", though they agreed it was "imperative to accelerate all diplomatic efforts to end the war". The participants' statement said they were asking the United Nations to bring together representatives of the Syrian government and opposition to launch "a political process leading to credible, inclusive, non-sectarian governance, followed by a new constitution and elections".