North Korea has vowed to launch a pre-emptive nuclear strike against the US, hours ahead of a UN vote on whether to level new sanctions against Pyongyang for its recent nuclear test. North Korea has accused the US of using military drills in South Korea as a launch pad for a nuclear war and has scrapped the armistice with Washington that ended hostilities in the 1950-53 Korean War. Al Jazeera's Dominic Kane reports.