Earlier this month, North Korea deliberately destroyed the information the International Atomic Energy Agency needed to analyze the fuel rods Pyongyang removed -- without appropriate IAEA supervision -- from its 25 megawatt reactor. As a result of this latest North Korean defiance of its obligations under the Non-Proliferation Treaty, we may never know with confidence whether it already has enough plutonium to make one or two nuclear weapons.

Now an even larger problem looms. These fuel rods, which currently are in cooling ponds, contain enough plutonium to make four to six nuclear weapons. In less than three months, they can be moved to North Korea's reprocessing facility at which the plutonium is separated from spent fuel. That "reprocessing" could take perhaps another three months. That means that by the end of this year, North Korea could have enough fissionable material for up to eight nuclear weapons.

We must not let that happen.

A hostile North Korea armed with a growing nuclear arsenal, already flight-testing missiles that can reach Japan and poised to export nuclear capabilities to countries such as Iran and Libya -- this would pose an unacceptable threat to our vital interests. It could substantially increase the risks facing our South Korean ally and the 37,000 U.S. military personnel stationed in Korea, undermine stability throughout East Asia, fuel a regional nuclear arms race and jeopardize the future of the NPT.

What to do? It is apparent that we cannot rely solely on IAEA safeguards to block North Korea's reprocessing of its spent fuel. North Korea has repeatedly demonstrated that it will flout its NPT obligations whenever it believes it serves its interests. Pyongyang's announcement Monday that it is withdrawing from the IAEA almost surely is intended as a warning that it is on the brink of pulling out of the NPT, expelling the IAEA inspectors and removing the IAEA's cameras and other safeguards. Pyongyang may believe that a perfect time to take this step would be when the fuel rods had cooled and were ready for reprocessing and that our threat to impose sanctions would be the perfect pretext. As things now stand, if Pyongyang implemented such a maneuver, we might never know whether it had gone ahead and reprocessed enough plutonium for another four to six nuclear weapons.

It also is hard to imagine that the "phased" economic sanctions being proposed by the United States -- if and when they are imposed -- could possibly be effective in time to slow or halt possible North Korea reprocessing plans.

The time has come for more decisive action. Specifically, the United States must make clear that whether Pyongyang remains in or withdraws from the NPT, the United States will not permit North Korea to reprocess its spent fuel. We should tell North Korea that it either must permit continuous, unfettered IAEA monitoring to confirm that no further reprocessing is taking place, or we will remove its capacity to reprocess.

In this connection, it should be noted that, aside from possible nuclear waste tanks, no nuclear material would be present in the reprocessing facility until the fuel rods were transferred from the cooling ponds. This means that the timely destruction of the reprocessing facility could entail far less risk of spreading radioactivity than would an attack on a nuclear reactor.

This approach is not intended to be provocative. On the contrary, it is designed to address the very real prospect that a single future act of North Korean defiance could make the already serious North Korean nuclear problem very much worse. The potential military action, if required, is intentionally quite limited and consciously designed to minimize the risks of unintentional damage.

It is worth re-emphasizing that the objectives of the proposed "no more reprocessing" policy also are limited. The approach we have outlined is designed to prevent a bad problem from becoming worse. By itself, it cannot deal with the one or two nuclear weapons North Korea may already have. That said, the policy's stated willingness to use military force if necessary should send Pyongyang an unmistakable signal of U.S. determination to resolve past North Korean nuclear transgressions as well as to preclude future nuclear threats.

At the same time, it is not risk-free. Some believe that any use of military force against North Korea could precipitate an attack against the South and launch a second Korean war. Indeed, North Korea has threatened that just the imposition of economic sanctions could provoke a North Korean military response. It therefore is imperative that we step up our efforts to strengthen U.S. and South Korean defensive military capabilities. Such a buildup not only would improve our ability to respond to any North Korean attack but also would reassure Seoul and Tokyo.

More generally, we should ensure that both our actions and our words make clear to Pyongyang that we will not be intimidated by its threats and will not be paralyzed by the possibility of war. On the contrary, Pyongyang must be made to understand that if war is unavoidable, we would rather fight it sooner than later, when North Korea might have a sizable nuclear arsenal. Likewise, it must understand that if war comes, it will result in the total defeat of North Korea and the demise of the Kim Il Sung regime.

The stakes could hardly be higher. The time for temporizing is over.

Brent Scowcroft was national security adviser to Presidents Ford and Bush. Arnold Kanter was in the State Department in the Bush administration. They are both with Forum for International Policy.