UN Syria envoy Staffan de Mistura asked Russia, Turkey and Iran to undertake urgent efforts to uphold the ceasefire regime in Syria and to smooth the way for peace talks. He has written a letter in this regard to the foreign ministers of Russia, Turkey and Iran. <br/><br/>A statement from his office yesterday said that the Special Envoy said that the ceasefire are indispensable for improving the conditions on the ground and contributing to an environment conducive for a productive political progress.