washington ban travel u.s. passport holders north korea take effect sept. americans country leave date u.s. state department say wednesday journalists humanitarian workers may apply exceptions ban department say public notice u.s. government last month say would bar americans travel north korea due risk long-term detention ban come time heighten tensions unite state north korea work develop nuclear-tipped missile capable hit unite state north korea become country americans ban travel american student otto warmbier sentence last year 15 years hard labor north korea return unite state coma june 13 release humanitarian ground die june 19. circumstances surround death clear include fell coma north korea say state media warmbier death mystery dismiss accusations die result torture beat captivity state department issue notice federal register wednesday declare u.s. passports invalid travel north korea restriction take effect 30 days apply one year unless extend revoke secretary state persons currently north korea u.s. passport depart north korea travel restriction enter effect friday september 2017 department say statement professional reporters journalists representatives international committee red cross american red cross travel official missions travel north korea compel humanitarian considerations whose request national interest may ask special validation passports order travel country state department say north korea currently hold two korean-american academics missionary canadian pastor three south korean nationals missionary work japan say north korea also detain least several dozen nationals u.s. ban travel north korea september say americans leave