kiev russian aggression blame violence eastern ukraine people die see hot war rather freeze conflict u.s. special envoy ukraine peace talk say visit ukraine sunday kurt volker former u.s. ambassador nato appoint current role july help resolve conflict ukrainian troop pro-russian separatists kill 10,000 people since 2014. washington cite conflict key obstacle good relations russia visit ukrainian-held town kramatorsk 690 km 430 miles southeast kiev volker say would prepare set recommendations washington good engage peace process freeze conflict hot war immediate crisis need address quickly possible say relations ukraine russia go freefall moscow 2014 annexation crimea subsequent outbreak pro-russian insurgency eastern donbass region ukraine accuse russian send soldier military equipment moscow deny volker reply affirmative ask whether saw conflict result russian aggression rather internal ukrainian factor see happen understand way conflict begin understand way manage today important unite state become engage fight donbass region kill 12 people particularly bloody week prompt germany france urge immediate progress implement ceasefire agreements sign belarus 2015 regularly flout leaders france germany ukraine russia speak phone monday discuss conflict u.s. secretary state rex tillerson say early july russia must make first move bring peace ukraine president petro poroshenko call powerful signal washington back career diplomat volker former aide republican senator john mccain russia hawk want unite state supply lethal weapons ukraine move previous administration barack obama shy away russia blame 'hot war ukraine u.s. special envoy