The North has substantial deposits of uranium ore and

it is much easier to secretly enrich uranium, which can be done in centrifuges rather than the nuclear reactor required for plutonium enrichment. Today's explosion had a yield of six to seven kilotons, South Korean defence ministry spokesman Kim Min-Seok told reporters, significantly more than the 2006 and 2009 tests, which both used plutonium. The explosive yield compared with 15 kilotons in the world's first atomic bomb dropped by the United States on the Japanese city of Hiroshima in 1945. North Korea's first test yielded less than one kiloton and was widely seen as a dud. The second test yielded between two and six kilotons, according to Seoul. The third test throws down a stark security and diplomatic challenge to Obama as well as to new Chinese leader Xi Jinping. Paik Hak-Soon, a North Korea expert at the Sejong Institute in Seoul, said Kim Jong-Un was intent on triggering a crisis that would force the international community to negotiate on his terms. "The UN is running out of options and probably knows new sanctions would only have a limited impact," Paik said. "The only real option for curbing further provocation is starting a dialogue with the North, but that will be very difficult given the domestic political pressure on leaders in the US, South Korea and Japan," Paik said. On top of uranium enrichment, a proven miniaturisation ability would take on added significance following December's rocket launch, which marked a major step forward in ballistic prowess, and provoked still-tighter UN sanctions. At the UN Security Council, the United States and its allies will push hard for China to get tough with its erratic ally. But China's leverage is limited, analysts say, by its fear of a North Korean collapse and the prospect of a reunified, US-allied Korea directly on its border. North Korea clearly violated UN resolutions by carrying out its latest nuclear test, the UN atomic agency said in a statement today. "I understand that the DPRK announced it had carried out a third test of a nuclear weapon, despite calls from the international community not to do so," Yukiya Amano, the head of the International Atomic Energy Agency, said in a statement. "This is deeply regrettable and is in clear violation of UN Security Council resolutions." (AFP) KUN 02121504 NNNN