North Korea today vowed to launch a pre-emptive nuclear strike against the United States, amplifying its threatening rhetoric hours ahead of a vote by UN diplomats on whether to level new sanctions against Pyongyang for its recent nuclear test.

An unidentified spokesman for Pyongyang's Foreign Ministry said the North will exercise its right for "pre-emptive nuclear strikes on the headquarters of the aggressors" because Washington is pushing to start a nuclear war against the North.

Although North Korea boasts of nuclear bombs and pre-emptive strikes, it is not thought to have mastered the ability to produce a warhead small enough to put on a missile capable of reaching the US It is believed to have enough nuclear fuel, however, for a handful of crude nuclear devices.

Such inflammatory rhetoric is common from North Korea, but it has been coming regularly in recent days. North Korea is angry over the possible sanctions and over upcoming US-South Korean military drills.