BEIJING , China ( CNN ) -- Senior North Korean officials say the communist regime has `` weaponized '' its stockpile of plutonium , according to a U.S. scholar , in a move suggesting that North Korea may have significantly hardened its stance on nuclear negotiations . Selig Harrison said North Korean officials claimed to have enough plutonium for four or five warheads . Selig Harrison , one of the few U.S. scholars granted access to senior North Korean officials , said at a news conference in Beijing that the officials told him they had weaponized 30.8 kilograms of plutonium , enough for four or five warheads . The director of the Asia Program at the Center for International Policy , who just returned from a five-day visit to Pyongyang , said senior North Korean officials told him the warheads will not be open for inspection . If it is true , the news portends a gloomy outlook for the future of the six-party talks that began in 2003 with the goal of getting North Korea to end its nuclear program . `` It does change the game , '' Harrison said . South Korea , the United States , Japan , China and Russia are participating in the talks . A 2007 agreement calls for scrapping nuclear weapons on the Korean peninsula in return for energy aid to the North , normalized relations between the North and the United States and Japan , and a formal peace pact . Watch a report on North Korea 's nuclear negotiations » . The North Koreans told Harrison they want the rest of the fuel aid that Japan has promised them . North Korea had agreed to disable the reactor that had produced plutonium for nuclear weapons . But the United States and its allies have asked it to give up the plutonium it already has , an estimated 30 kilograms , as well as details of any other bomb-producing programs . Harrison said one possible reason for Pyongyang 's tough new stance could be the declining health of leader Kim Jong Il , who reportedly suffered a stroke last year and may no longer be involved in day-to-day decisions . `` People I talked to have many indications that some important things are submitted to him , but he is not working in the way he used to , '' Harrison said . He said military hard-liners have taken the lead in demanding from the United States a full declaration and verification of all nuclear weapons sent to South Korea between 1957 and 1991 . The hard-liners also seek full normalization of relations with Washington before more talks about scrapping their nuclear arsenal . On Tuesday , during her Senate confirmation hearing for the secretary of state position , Sen. Hillary Clinton made it clear : de-nuclearization first , then diplomatic normalization . President-elect Barack Obama has stated his willingness to talk to the North Korean leader . Harrison also said the North demanded the completion of the light-water reactors as compensation for the dismantling of the Yongbyon nuclear reactor . The light-water reactor , which is not capable of producing weapons-grade plutonium , was promised to North Korea in the early 1990s for the North giving up its nuclear weapons . Its construction has been suspended . North Korea has long considered its nuclear program integral to its national security . North Korea tested a nuclear weapon in 2006 . In June , it acknowledged producing about 40 kilograms of enriched plutonium . CNN 's John Vause contributed to this report .
News may bode well for future of talks to end North Korean nuclear program . North Korean officials tell U.S. scholar they want rest of promised fuel aid . Another possible reason for tough ##ness could be poor health of leader Kim Jong Il . Military hard - line seek normalization of relations with China before more talks .