berlin german chancellor angela merkel u.s. president donald trump condemn north korea nuclear test monday urge unite nations quickly agree tough sanction pyongyang german government spokesman say agree test hydrogen bomb mean new unacceptable escalation north korean regime steffen seibert say statement speak telephone german chancellor american president express view international community must continue exert pressure regime north korea unite nations security council quickly adopt strict sanction seibert add part merkel tell trump germany would push tough sanction north korea european union seibert say add aim dissuade north korea violations international law achieve peaceful solution conflict merkel trump call tough u.n. sanction north korea