washington u.s. secretary state rex tillerson say friday north korea continue missile test threaten entire world stress unite state work closely regional ally japan south korea problem east asia increasingly aggressive isolate regime north korea threaten democracies south korea japan importantly recently expand threats unite state endanger entire world tillerson say gather community democracies first look regional ally south korea japan work democratic partner continue build consensus unite nations security council create unite international front uphold value strive make us safe tillerson say north korea 's aggression endanger 'entire world