North Korea announced on Wednesday it has successfully carried out a nuclear fusion experiment in a further development of cutting-edge nuclear technology, the Yonhap news agency reported. Although North Korean leader Kim Jong-il has repeatedly stated his commitment to denuclearization of the Korean Peninsula, the reclusive communist regime appears to be making a steady progress in nuclear research and development. "Nuclear fusion is a breakthrough event that shows North Korea's cutting-edge technology that is leaping forward," Yonhap quoted N. Korea's Rodong Sinmun newspaper. Nuclear fusion could be used to develop thermonuclear weapons, which are much more powerful than weapons based on nuclear fission. Only six countries-United States, Russia, United Kingdom, People's Republic of China, France and India-have conducted thermonuclear weapon tests. North Korea withdrew from the Nuclear Non-Proliferation Treaty (NPT) in 2003 and has since held two nuclear tests as well as a number of ballistic missile tests. North Korea is banned from conducting nuclear or ballistic tests under UN Resolution 1718, adopted after North Korea's first nuclear test on October 9, 2006. However, Pyongyang carried out a second nuclear test on May 25, 2009, followed by a series of short-range missile launches, and has threatened to build up its nuclear arsenal to counter what it calls hostile U.S. policies. Talks on North Korea's nuclear program, involving Russia, Japan, China, the United States and the two Koreas, stalled last April when Pyongyang pulled out of the negotiations in protest against the United Nations' condemnation of its missile tests. Pyongyang insists that a peace treaty on the 1950-1953 Korean War between the United States and North Korea needs to be signed before there is even any thought of Korea getting rid of its nuclear weapons.