unite nations top myanmar official appeal monday democracy country give chance survive amid international anger military campaign rohingya muslims unite nations describe ethnic cleanse 507,000 rohingya muslim flee bangladesh since insurgents attack security post near border aug. 25 trigger fierce myanmar military retaliation myanmar say 500 people kill insurgents national security adviser thaung tun tell reuters speak u.s. counterpart h.r mcmaster phone visit members u.s. congress washington last week say sanction specifically discuss unite state call last week countries suspend provide weapons myanmar military stop short threaten reimpose u.s. sanction suspend obama administration need ensure democracy chance survive myanmar young democracy thaung tun tell reuters interview unite nations note government leader nobel peace laureate aung san suu kyi office 18 months suu kyi assume power follow landslide election win former military leaders initiate political transition years unite state others impose sanction myanmar support suu kyi campaign democracy lot challenge challenge overcome day rome build day undo 50 years challenge say thaung tun add hop meet person mcmaster president donald trump national security adviser brief current situation trump administration official say last month violence make hard unite state myanmar build warm tie would likely ease short term expect return sanction thaung tun say meet privately u.s. ambassador unite nations nikki haley speak briefly sideline meet new york u.n. security council meet publicly last week myanmar first time since 2009. haley say myanmar authorities appear carry brutal sustain campaign cleanse country ethnic minority say countries stop supply weapons myanmar military sufficient accountability measure thaung tun say action take number policemen exceed bound deal detainees strict instructions security force carry duties within bound code conduct say nobody law say ethnic cleanse genocide happen myanmar myanmar government say military operations since sept. 5. thaung tun say since security force respond attack cover night sporadic attack police security people require respond self-defense say rohingya deny citizenship classify illegal immigrants despite claim root myanmar go back centuries communities marginalize subject bouts communal violence years bangladesh myanmar agree monday set work group plan repatriation flee story refiled correct national security adviser name second reference thereafter thaung tun tun top myanmar official say 'young democracy face challenge