U.N. envoy calls on powers to salvage Syrian ceasefire

By Stephanie NebehayGENEVA (Reuters) - U.N. Syria envoy Staffan de Mistura called on Russia, Turkey and Iran on Saturday to salvage the tattered ceasefire in Syria thatwould also help keep peace talks on track.Syrian President Bashar al-Assad and his allies, Russia, Iran and Shi'ite militias from nearby countries, are seeking to staunch the biggest rebel assault in months, which began this week in the capital Damascus and the Hama countryside.