washington/moscow u.s. president donald trump russian president vladimir putin tuesday move ease tension u.s. air strike april russian ally syria express desire syrian ceasefire safe zone civil war refugees two leaders speak phone first time since u.s. relations russian strain u.s. attack syrian airfield two leaders set foundation could first face-to-face meet july statements white house kremlin suggest two leaders productive conversation include north korea fight islamist militants throughout middle east senior trump administration official say putin request call describe effort present ideas syria trump order 59 cruise missiles launch retaliation chemical weapons attack unite state blame syrian president bashar al-assad attack prompt protest assad ally russia blame syrian rebel use outlaw nerve gas say assad fault white house say two leaders agree party must end violence syria conversation good one include discussion safe de-escalation zone achieve last peace humanitarian many reason white house statement say trump presidential campaign last year frequently say want safe zone establish syrian refugees pay gulf state alleviate need refugees move elsewhere include unite state candidate trump also express desire u.s. alliance russia fight islamist militants goal elusive since take office jan. 20. ceasefire ever elusive syria white house say washington would send representative ceasefire talk astana kazakhstan wednesday thursday state department say act assistant secretary near eastern affairs stuart jones attend observer decision send jones talk even observer indication unite state take astana talk seriously previously u.s. ambassador kazakhstan george krol attend talk observer kremlin say putin trump agree step dialogue find ways strengthen ceasefire give stability aim create condition launch real resolution process syria mean russian foreign minister u.s. secretary state effectively inform leaders progress direction white house statement say trump putin also speak best resolve dangerous situation north korea north korea nuclear ballistic missile program pose major global challenge two leaders also discuss go resolve crisis raise tensions throughout asia-pacific trump tell reuters interview last week major major conflict possible north korea amping pressure pyongyang stand china rein north dangerous situation korean peninsula discuss detail vladimir putin call restraint level tension reduce kremlin say two leaders also discuss first face-to-face meet sideline g20 summit hamburg july 7-8 kremlin say trump putin discuss syria ceasefire first talk since u.s. air strike