Dating back to the Bush administration, the United States has been determined to monitor the development of nuclear weapons in other countries in concert with the United Nations. Similarly, President Clinton has pledged to give the highest priority to stemming the spread of weapons of mass destruction.

Unfortunately, the International Atomic Energy Agency, a U.N. affiliate, failed to detect or prevent Iraq's nuclear weapons program prior to the Persian Gulf War.And while most of the U.N. attention since then has been focused on Iraq, some disturbing intelligence reports are coming out of North Korea, another country run by a hard-line dictatorship.

Those reports suggest a secret effort to develop nuclear weapons. Western diplomats say North Korea has probably already produced more weapons-grade plutonium than it is acknowledging.

Only a few months ago, the threat of North Korea's nuclear program seemed to have been diffused by international safeguards and North Korea's willingness to accept in-ter-na-tional inspections. Now that has all changed.

Nuclear scientists say it takes about 18 pounds of plutonium to produce a nuclear weapon, and North Korea has given assurances that it has nothing close to that level.

But a recent inspection of plutonium produced by North Koreans has led experts to conclude that the North Koreans have more plutonium than they have admitted.

Intelligence reports also express concern about two suspected nuclear waste sites near the Yongbyon reactor in North Korea, where it is feared enough irradiated materials have been removed to produce plutonium.

Even though the Atomic Energy Agency has asked to be allowed to inspect those sites, the North Koreans have thus far refused to comply.

Such refusal prompts American officials to fear the worst and with good reason. The natural inference drawn is that if they won't allow inspection, there are things they don't want inspectors to discover.

There is recourse. If North Koreans persist in refusing, the agency could demand "a special inspection," an extraordinary procedure that has never been used before.

If they still refuse, the matter could be referred to the U.N. Security Council, where there is no precedent for what action might be taken. If it goes that far, it is critical that the U.N. order the inspection and that North Korea comply.

If one country - no matter what country it is - is allowed to produce nuclear weapons without international inspection, it will effectively negate the international position on the issue, and such countries as Iran, Libya and others will undoubtedly become major problem cases, and instruments of mass destruction will proliferate.