North Korea has said it would begin a "sacred war" against the United States and South Korea at "any time necessary" based on its nuclear deterrent, in response to "reckless" military exercises by the allies. North Korea has driven tensions on the Korean peninsula to new heights after the South accused it of sinking one of its warships in March, killing 46, and took steps to boost its defence including massive military drills with the US. Pyongyang voiced shrill anger in the past when the allies conducted exercises, but US officials said further provocations are possible, especially as the North tries to build political momentum for succession of power to Kim Jong-il's son. US and South Korean militaries begin large-scale naval and aerial drills on Sunday with a nuclear-powered aircraft carrier taking part and they have additional exercises planned in August. On North Korea's state run television station KRT, a newsreader quoted the National Defence Commission as saying: "The army and people of the DPRK will start a retaliatory sacred war of their own style based on nuclear deterrent any time necessary in order to counter the US imperialists and the South Korean puppet forces deliberately pushing the situation to the brink of a war." Washington brushed off the latest threat and said it had no interest in getting into a war of words. A State Department spokesman said What the US needed from North Korea was fewer provocative words and more constructive action. The North Korean statement continued: "All these war maneuvers are nothing but outright provocations aimed to stifle the DPRK by force of arms to all intents and purposes." It again denied that the country was behind the sinking of South Korea's corvette Cheonan, and said the planned military drills were "as reckless an act as waking up a sleeping tiger."