South Korea denounced its northern neighbour Tuesday for putting the Korean Peninsula under the threat of nuclear conflict because of its rejection of non-proliferation principles. "The integrity and credibility of the Nuclear Non-proliferation Treaty has suffered an irreparable blow as a result of North Korea's complete disregard for and defiance of all nuclear non-proliferation norms," South Korean Deputy Foreign Minister Chun Yung-woo said at a conference to review the treaty, or NPT, at U.N. headquarters in New York, DPA reported. "The North Korean nuclear issue poses an unacceptable threat to peace and security on the Korean Peninsula," he said. Pyongyang withdrew from the NPT in 2003 and this year announced it holds nuclear weapons. It has refused to return to the six-nation nuclear talks mediated by China that aim to persuade the North Koreans to end their nuclear activities. China, the United States, Russia, the two Koreas and Japan are the six parties in the talks. Russian Deputy Foreign Minister Sergey Kislyak maintained, however, that the "nuclear problem" in North Korea could be solved through the six-nation talks. "We believe that the North Korean return to the NPT is not only possible, but virtually essential," Kislyak told the conference.