The U.S. demanded that Syrian leader Bashar al-Assad's forces halt their bombardment of the city of Aleppo and help restore a nationwide ceasefire In calls to the UN peace envoy for Syria and to the lead opposition negotiator, US Secretary of State Kerry said the priority was  a durable, nationwide cessation. A truce was called in February between Assad's forces and a coalition of rebels but has been breaking down in the divided and besieged city of Aleppo