United Nations chief Ban Ki-moon said Wednesday he was determined to achieve a nuclear-free North Korea amid tension over new UN sanctions against the isolated communist regime. 'I spare no effort in facilitating the achievement of verifiable denuclearisation of the Korean peninsula,' Ban told a news conference after holding talks with Japanese Prime Minister Taro Aso in Tokyo. Pyongyang has warned that 'dark clouds of nuclear war' are gathering after the United Nations strengthened sanctions against it following its atomic test in May. The North has responded defiantly to the UN move, by vowing to build more nuclear bombs. Aso echoed Ban's comments, saying: 'North Korea's ballistic missile launches and nuclear tests are a serious threat to the international community. We will never allow North Korea's nuclear weapons possession.' The new sanctions include calling on UN member states to inspect ships if they suspect these are carrying banned weapons to or from the North. Pyongyang said Wednesday it would hit back against any attempt to search its vessels, as a Pentagon official said a North Korean ship, the first to be tracked under the new sanctions, has changed course after being followed by the US Navy on suspicion of carrying weapons. The US official declined to say where the Kang Nam 1, which left home on June 17, was now headed after it was reported to be originally bound for Myanmar. On Wednesday North Korea warned of military action against its arch-enemy Japan should Tokyo stop its vessels for cargo inspections. Rodong Sinmun, the ruling communist party's daily newspaper, said Tokyo was pushing for a new law to authorise tougher searches. But in a commentary Rodong said: 'Our ships are sacred and impregnable places where our sovereignty reigns. If anyone hurts them, it would be considered a grave military provocation against us. 'This kind of action will immediately meet with our self-defensive military actions and the responsibility for all consequences will rest with Japan.' Japan, along with the United States, pushed hard for tough sanctions after the North's long-range rocket launch on April 5 and its second underground atomic test on May 25. North Korea issued a fresh warning Wednesday to Japan to stay clear of some of its coastal areas when Pyongyang conducts military exercises this month, the Japan Coast Guard said. The emailed message was seen as signalling more possible short-range missile tests at a time when North Korea is also thought to be preparing a long-range missile launch into Pacific waters, short of Hawaii. The warning came a day after Washington ordered sanctions on an Iranian-based firm named Hong Kong Electronics for allegedly aiding the North's missile programme, and accused the two nations of joint arms proliferation. The US Treasury said the company had been 'providing support to North Korea's Tanchon Commercial Bank and Korea Mining Development Trading Corp (KOMID). A statement said Hong Kong Electronics has since 2007 'transferred millions of dollars of proliferation-related funds on behalf of Tanchon and KOMID' and has 'facilitated the movement of money from Iran to North Korea on behalf of KOMID.' Meanwhile, the UN's food aid agency said North Koreans, especially children, faced a 'critical' food situation as donations had dried up. Torben Due, the World Food Programme's country representative in North Korea, said Pyongyang had told the agency to scale back its operations in the impoverished country, without giving clear reasons. He said the WFP had to pare back its goal of reaching 6.2 million people and was now targeting just 2.27 million. burs-elw/hg 