WHEN North Korea signed the Nuclear Non-Proliferation Treaty in 1985, it accepted the obligation to negotiate a safeguards agreement with the International Atomic Energy Agency (IAEA) in Vienna. Such an agreement would allow international inspectors access to North Korea's nuclear plants to assure that all activities were for peaceful purposes. Six years have now passed without North Korea living up to its obligations to sign such an agreement.After several years of protracted negotiations, North Korean Foreign Minister Kim Yong Nam announced that the final touches on the text have been completed. But then Pyongyang invented another reason for delay. North Korea linked signing the safeguards agreement to the withdrawal of United States nuclear forces from South Korea and American promises not to use nuclear arms against the North. A statement from the North Korean Observer Mission at the UN announced in 1990 that North Korea would sign the saf eguards agreement "at any moment," but added "only on condition that the US gives legal assurances" it would not resort to threats of nuclear use. Even before George Bush's September speech announcing the withdrawal of tactical nuclear weapons, US military experts concluded the US could effectively defend South Korea without nuclear weapons. North Korean Foreign Minister Kim said President Bush's announcement was "really welcome news for us." But the fact that North Korea still drags its heels about signing the completed safeguards agreement has renewed suspicions that Pyongyang is playing for time to develop a bomb. Both Kim and North Korean Prime Minister Yon Yong Muk deny this. Kim argued that "if our current nuclear research facilities are opened, they will realize the Koreans have nothing." IN 1964, the Soviet Union supplied North Korea with a small, four-megawatt research reactor that was placed under IAEA inspection in 1977. It is not a source of concern. Worries developed in the 1980s, when North Korea built a 30-megawatt gas-graphite research reactor that used natural uranium and could produce enough plutonium for a nuclear weapon each year. Such a reactor seemed unduly large for civilian research, and was similar to the reactors used by India and Israel. Such a reactor would not pose a problem, however, unless there were a means of extracting the plutonium from its spent fuel. In recent years, North Korea has been building a large facility in Yongbyon that could be a reprocessing plant. While it is not complete, and there are different opinions among intelligence analysts about its purpose, many believe it is a reprocessing plant that will provide the missing link in nuclear-weapons production. In addition, North Korea seems to have started a third, larg er reactor that will also be fueled by natural uranium, and thus well suited for plutonium production. Since there is no credible nonmilitary use for plutonium in North Korea's nuclear program, the outside suspicions seem justified. It is just such suspicions that international inspections under the IAEA are meant to address. If North Korea wants other states to believe its denials that it is developing nuclear weapons, there is a simple step it could take: Sign the safeguards agreement and allow the international inspectors access to its suspect plants. After the way Iraq cheated on its treaty obligations and lied to the rest of the world, the international community is unlikely to be satisfied with statements not verified by inspe ctions. The new US policy on removing tactical nuclear weapons undercuts any North Korean excuses for delay. North Korea recently joined the UN and may have more interest in emerging from its self-imposed isolation. It wants Japanese economic assistance. To achieve these objectives, it will need to reassure the international community about its nuclear program. The best way to do that would be to promptly sign the safeguards agreement and allow the IAEA inspection that it agreed to when it signed the Non-Prolife ration Treaty six years ago.