North Korea has vowed to launch a pre-emptive nuclear strike against the United States, hours ahead of a U.N. vote on whether to level new sanctions against Pyongyang for its recent nuclear test.

North Korea has accused the U.S. 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.

“Since the United States is about to ignite a nuclear war, we will be exercising our right to pre-emptive nuclear attack against the headquarters of the aggressor in order to protect our supreme interest,” the North’s foreign ministry spokesman said in a statement carried by the official KCNA news agency.

The North conducted a third nuclear test on Feb. 12, in defiance of U.N. resolutions, and declared it had achieved progress in securing a functioning atomic arsenal.

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 U.S. mainland.

It is believed to have enough nuclear fuel, however, for a handful of crude nuclear devices.

The North’s unnamed foreign ministry spokesman also said it would be entitled to take military action as of Mar. 11 when U.S.-South Korea military drills move into a full-scale phase, as it had declared the truce invalid.

It is the latest in an escalation of tough words from both sides of the armed Korean border this week as the U.N. Security Council deliberates a resolution to tighten financial sanctions and a naval blockade against the North.

U.S. double standards

North Korea, which held a mass military rally in Pyongyang on Thursday in support of its recent threats, has protested against the U.N. censures of its rocket launches.

It says they are part of a peaceful space programme and that the criticism is an exercise of double standards by the U.S.

In 2010, the North bombed South Korea’s Yeonpyeong Island killing two civilians. It is widely accused of sinking a South Korean navy ship earlier in the year, killing 46 sailors.

North Korea was conducting a series of military drills and getting ready for state-wide war practice of an unusual scale, South Korea’s defence ministry said earlier on Thursday.

South Korea and the U.S., which are conducting annual military drills until the end of April, are watching the North’s activities for signs they turn from an exercise to an actual attack, a South Korean official said.

“It hasn’t been frequent that the North conducted military exercise at the state level,” South Korea’s defence ministry spokesman, Kim Min-seok, said.

“We are watching the North’s activities and stepping up readiness under the assumption that these drills can lead to provocation at any time.”

A top North Korean general said on Tuesday that Pyongyang was scrapping the armistice. But the two sides remain technically at war, as the war did not end with a treaty.

South Korea’s military said in a rare warning on Wednesday that it would strike back at the North and target its leadership if Pyongyang launched an attack.

* Published under an agreement with Al Jazeera.