For several years, North Korea has said it had nuclear weapons and the world has generally assumed that it did. With Pyongyang's apparent underground detonation of such a device on Monday, whatever lingering uncertainty there may have been has dissipated. Call it Kim Jong-Il's coming-out party. Now the question of what to do about one of the most dangerous regimes on the planet - a state-sponsor of terror who has expressed a willingness to sell its nuclear technology to those with the cash to buy it - recurs with fresh urgency.

Let's get one thing straight at the outset: The threat North Korea poses today is actually not appreciably different from that the Stalinist regime constituted last week. The difference is that we no longer have the luxury of ignoring it, or dealing with it through feckless "six-party talks," which amounts to the same thing.

Instead, we need to approach the danger posed by a nuclear-armed North Korea as though it constitutes a mortal peril to American strategic interests in Asia and, perhaps, to this country directly, as well. For, indeed, it does. The idea that a regime that has permitted some two million of its own people to starve to death will better treat others - including ours - is untenable and risky in the extreme.

Consequently, we need now to hold accountable those responsible for the North Korean nuclear program. Communist China has been playing a double-game for years. Without Beijing's military technology, to say nothing of its financial support, strategic protection and food and energy life-lines, Kim Jong-Il's regime would have been toast long ago and its people likely reunited with prosperous South Korea. To a lesser degree, the same can be said of the role played by Vladimir Putin's Russia.

Pakistan was the cut-out for much of the nuclear weapons know-how and equipment that flowed from China to Pyongyang. Nukes-r-Us impresario A.Q. Khan appears to have been used in transfers for which the Pakistani regime sought plausible deniability.

More recently, Iran has been an enabler of North Korea's nuclear and missile programs. Call it the oil-for-weapons program. Pyongyang has been trading mass destruction wherewithal and delivery systems to Tehran in exchange for energy supplies and, presumably, cash. The deal has helped lubricate Kim's steady progress towards ever-longer-range missiles and his acquisition of weapons to go on them. It has also greatly shortened the length of time it is taking Iran, the other charter member of the "Axis of Evil," to get up the learning curve in both areas.

Unfortunately, even our nominal ally, South Korea has become increasingly vital to propping up Kim's regime. It is investing substantial sums in the North, creating industrial zones there for which it has been seeking special treatment in trade arrangements with the United States and otherwise demanding that Pyongyang be appeased by the West.

These sorts of activities can no longer be either ignored or tolerated. While the United States is going to have to pick its shots, it must now adopt the sort of strategy Ronald Reagan employed to destroy the Soviet Union: A concerted campaign aimed at cutting off the funding to, neutralizing the threat from and de-legitimating a hostile regime. Elements of such a campaign would include the following:

Joining with Japan, Australia and others who share our view of the danger posed by North Korea to deny Pyongyang the financial life-support it must have to survive. International corporations operating in the North should be given a choice: Do business with Kim or with the Free World. Those who opt for the former should be denied government contracts, subjected to financial sanctions and import controls and made the focus of divestment initiatives like that which ultimately brought down the South African regime twenty years ago.

Greatly ramping up the U.S. effort to deploy the sort of effective anti-missile defenses first sought by Mr. Reagan in 1983. Thanks to President Bush's leadership, the United States now has the latitude to protect its people against ballistic missile attack. To date, unfortunately, the effort to do so has mostly been confined to a limited, land-based missile defense system. In light especially of the North Korean threat, we need to augment that deployment immediately by modifying the Navy's Aegis fleet air-defense ships with the capability to shoot down ballistic missiles of various ranges - whether launched from places like North Korea or from tramp steamers off our coasts.

In addition, now that the North Koreans have joined the Indians and Pakistanis in demonstrating that our restraint in nuclear testing is not preventing others from doing such experimentation, we need to resume the sort of periodic underground tests essential to ensuring that our deterrent remains as safe, reliable and credible as we can make it. President Reagan strenuously argued that such testing is a non-negotiable requirement. We can no longer responsibly persist in the moratorium on nuclear testing we have observed since 1992.

Finally, the United States must stop pretending that Kim Jong-Il's regime is one with which we can live. Rather than legitimating the regime by negotiating with it - even in multilateral settings, to say nothing of bilateral ones, every effort should now be bent towards discrediting this odious dictatorship, making pariahs of those who perpetuate it and encouraging freedom throughout the Korean peninsula.

President Reagan demonstrated that the peoples enslaved by the Soviet superpower need not be consigned to such a state in perpetuity. So in our time we must bend every effort to ending the tyrannical misrule of the nuclear club's newest, and arguably most dangerous, member: Kim Jong-Il.