SEOUL (AFP) - North Korea threatened Wednesday to conduct a second nuclear test unless the United Nations apologises for condemning its rocket launch, sharply raising the stakes in the dispute over its weapons programmes. Unless the Security Council apologises immediately, the North vowed to take what it called additional defensive measures. The measures will include nuclear tests and test-firings of intercontinental ballistic missiles, its Foreign Ministry said in a statement on official media. The announcement further raised regional tensions following the Norths April 5 launch of a long-range rocket. Pyongyang said it put a peaceful satellite into orbit while other nations saw a disguised missile test. The Security Council condemned the launch and ordered tougher enforcement of sanctions imposed in 2006 after the Norths missile launch and first nuclear test earlier that year. The communist state reacted angrily, announcing it was quitting a six-nation nuclear disarmament pact and restarting the plants at Yongbyon which produced weapons-grade plutonium. Wednesdays statement blasted the assets freeze as an infringement of its sovereignty. Progress on the pact - which the North has now abandoned - was stalled by disagreement over how to verify the Norths declared nuclear activities. The statement also announced plans to build a light-water nuclear reactor and said it would start developing technology to produce fuel for it. The Ministry denounced the Security Council for illegal provocations by imposing sanctions on the three firms. Such measures would not work, it asserted, because North Koreans have for decades lived under sanctions and blockade by hostile forces. Hope of denuclearising the Korean peninsula have now gone forever and the situation is inching to the brink of war by the hostile forces, it said. Chinese Premier Wen Jiabao and his Japanese counterpart Taro Aso said the world community should not overreact and agreed that the six-nation talks remained the best forum for achieving denuclearisation, a Japanese official at their meeting in Beijing told journalists. In Washington, the United States warned North Korea that it is deepening its international isolation with threats to carry out a second nuclear test. Let me just say very clearly that these threats only further isolate the North, State Department spokesman Robert Wood said after Pyongyang vowed to stage the test unless the United Nations apologises for condemning its rocket launch. I dont think youll see an apology from the Security Council, Wood said. Wood said the US was working with its partners in the six-way talks involving the two Koreas, the United States, Japan, China and Russia in order to find a way to bring Pyongyang back to the negotiations.