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 the 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 is leaping forward," Yonhap quoted North Korea`s Rodong Sinmun newspaper as saying. Nuclear fusion could be used to develop thermonuclear weapons, which are much more powerful than weapons based on nuclear fission. Only six countries -the United States, Russia, the United Kingdom, 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.