North Korean technicians are reportedly in the final stages of fueling a long-range ballistic missile that some experts estimate can deliver a deadly payload to the United States. The last time North Korea tested such a missile, in 1998, it sent a shock wave around the world, but especially to the United States and Japan, both of which North Korea regards as archenemies. They recognized immediately that a missile of this type makes no sense as a weapon unless it is intended for delivery of a nuclear warhead.

A year later North Korea agreed to a moratorium on further launches, which it upheld -- until now. But there is a critical difference between now and 1998. Today North Korea openly boasts of its nuclear deterrent, has obtained six to eight bombs' worth of plutonium since 2003 and is plunging ahead to make more in its Yongbyon reactor. The six-party talks aimed at containing North Korea's weapons of mass destruction have collapsed.

Should the United States allow a country openly hostile to it and armed with nuclear weapons to perfect an intercontinental ballistic missile capable of delivering nuclear weapons to U.S. soil? We believe not. The Bush administration has unwisely ballyhooed the doctrine of "preemption," which all previous presidents have sustained as an option rather than a dogma. It has applied the doctrine to Iraq, where the intelligence pointed to a threat from weapons of mass destruction that was much smaller than the risk North Korea poses. (The actual threat from Saddam Hussein was, we now know, even smaller than believed at the time of the invasion.) But intervening before mortal threats to U.S. security can develop is surely a prudent policy.

Therefore, if North Korea persists in its launch preparations, the United States should immediately make clear its intention to strike and destroy the North Korean Taepodong missile before it can be launched. This could be accomplished, for example, by a cruise missile launched from a submarine carrying a high-explosive warhead. The blast would be similar to the one that killed terrorist leader Abu Musab al-Zarqawi in Iraq. But the effect on the Taepodong would be devastating. The multi-story, thin-skinned missile filled with high-energy fuel is itself explosive -- the U.S. airstrike would puncture the missile and probably cause it to explode. The carefully engineered test bed for North Korea's nascent nuclear missile force would be destroyed, and its attempt to retrogress to Cold War threats thwarted. There would be no damage to North Korea outside the immediate vicinity of the missile gantry.

The U.S. military has announced that it has placed some of the new missile defense interceptors deployed in Alaska and California on alert. In theory, the antiballistic missile system might succeed in smashing into the Taepodong payload as it hurtled through space after the missile booster burned out. But waiting until North Korea's ICBM is launched to interdict it is risky. First, by the time the payload was intercepted, North Korean engineers would already have obtained much of the precious flight test data they are seeking, which they could use to make a whole arsenal of missiles, hiding and protecting them from more U.S. strikes in the maze of tunnels they have dug throughout their mountainous country. Second, the U.S. defensive interceptor could reach the target only if it was flying on a test trajectory that took it into the range of the U.S. defense. Third, the U.S. system is unproven against North Korean missiles and has had an uneven record in its flight tests. A failed attempt at interception could undermine whatever deterrent value our missile defense may have.

We should not conceal our determination to strike the Taepodong if North Korea refuses to drain the fuel out and take it back to the warehouse. When they learn of it, our South Korean allies will surely not support this ultimatum -- indeed they will vigorously oppose it. The United States should accordingly make clear to the North that the South will play no role in the attack, which can be carried out entirely with U.S. forces and without use of South Korean territory. South Korea has worked hard to counter North Korea's 50-year menacing of its own country, through both military defense and negotiations, and the United States has stood with the South throughout. South Koreans should understand that U.S. territory is now also being threatened, and we must respond. Japan is likely to welcome the action but will also not lend open support or assistance. China and Russia will be shocked that North Korea's recklessness and the failure of the six-party talks have brought things to such a pass, but they will not defend North Korea.

In addition to warning our allies and partners of our determination to take out the Taepodong before it can be launched, we should warn the North Koreans. There is nothing they could do with such warning to defend the bulky, vulnerable missile on its launch pad, but they could evacuate personnel who might otherwise be harmed. The United States should emphasize that the strike, if mounted, would not be an attack on the entire country, or even its military, but only on the missile that North Korea pledged not to launch -- one designed to carry nuclear weapons. We should sharply warn North Korea against further escalation.

North Korea could respond to U.S. resolve by taking the drastic step of threatening all-out war on the Korean Peninsula. But it is unlikely to act on that threat. Why attack South Korea, which has been working to improve North-South relations (sometimes at odds with the United States) and which was openly opposing the U.S. action? An invasion of South Korea would bring about the certain end of Kim Jong Il's regime within a few bloody weeks of war, as surely he knows. Though war is unlikely, it would be prudent for the United States to enhance deterrence by introducing U.S. air and naval forces into the region at the same time it made its threat to strike the Taepodong. If North Korea opted for such a suicidal course, these extra forces would make its defeat swifter and less costly in lives -- American, South Korean and North Korean.

This is a hard measure for President Bush to take. It undoubtedly carries risk. But the risk of continuing inaction in the face of North Korea's race to threaten this country would be greater. Creative diplomacy might have avoided the need to choose between these two unattractive alternatives. Indeed, in earlier years the two of us were directly involved in negotiations with North Korea, coupled with military planning, to prevent just such an outcome. We believe diplomacy might have precluded the current situation. But diplomacy has failed, and we cannot sit by and let this deadly threat mature. A successful Taepodong launch, unopposed by the United States, its intended victim, would only embolden North Korea even further. The result would be more nuclear warheads atop more and more missiles.

Ashton B. Carter was assistant secretary of defense under President Bill Clinton and William J. Perry was secretary of defense. The writers, who conducted the North Korea policy review while in government, are now professors at Harvard and Stanford, respectively.

For Vice President Dick Cheney, the question of how to deal with would-be nuclear powers in Iran and North Korea is disarmingly simple.

"We don't negotiate with evil; we defeat it,'' Cheney reportedly pronounced, dismissing a State Department bid in late 2003 to make a deal with North Korea. A similar prescription was offered when moderates in the Iranian regime made a secret approach that year to begin talks with the United States.

The long history of the Cold War is replete with the issue of whether -- and how -- to talk with a mortal foe. U.S.-Soviet relations froze time and again. For two decades, there was no dialogue at all with Communist China. But in the end, American policymakers have always chosen the path of negotiation.

For Cheney -- and for President George W. Bush -- sitting down at a table with the likes of North Korea's Kim Jong Il would be an act of weakness, a lessening of American power and prestige that granted undeserved legitimacy to despised regimes.

In recent months, and most prominently last week, the Bush administration has appeared to reverse its stance, opening the door to direct talks with North Korea and Iran.

These moves are carefully constrained, reflecting in part the ongoing divisions in the Bush administration about the advisability of going down this path. Contacts with both regimes will take place only within the framework of multilateral talks and focused solely on the issue of their nuclear programs. One-on-one talks on a broader agenda, including establishing basic diplomatic relations, have been explicitly ruled out, for now.

The decision to talk seems driven in large part by the realization that defeating evil has proven to be more difficult than some in the administration assumed. After Iraq, the use of military force against Iran -- and even more so against a North Korea already probably armed with nuclear weapons -- is highly unlikely. Potential allies in imposing economic and political sanctions -- the Europeans, Russians and Chinese, along with South Korea and Japan -- won't even consider such steps without a greater show of American willingness to negotiate with the evil enemy.

Limited as it is, the significance of this shift has to be seen against the backdrop of deep resistance to such diplomatic engagement in the Bush administration.

"There is a fundamental disagreement over how to approach the North Korea problem,'' explained Richard Armitage, who served as deputy secretary of state from 2001-05.

"'Those of us at the State Department concluded: From the North Korean point of view, the nuclear issue is the only reason we Americans talk with them,'' Armitage recounted in a recent interview with the Oriental Economist newsletter. "Therefore, the North Koreans would be very reluctant to let go of the nuclear program. We knew it was going to be a very difficult process. But you have to start somewhere. You start by finding out what their needs and desires are, and seeing if there is a way of meeting those needs and desires without giving away something that is sacred to us.''

But the White House and others in the administration blocked at every turn their attempts to open direct dialogue with Pyongyang. "There is a fear in some quarters, particularly the Pentagon and at times in the vice president's office, that if we were to engage in discussions with the North Koreans, we might wind up with the bad end of the deal,'' Armitage said. "They believe that we should be able to pronounce our view, and everyone else, including the North Koreans, should simply accept it. This is not a reasonable approach.''

Six-party talks

The compromise was the decision, through the good offices of China, to convene six-party talks that included surrounding countries such as Russia, South Korea and Japan. Administration officials have argued that this format rallies others to back the United States in pressing the North Koreans, effectively isolating them.

The same argument was made for the United States to support, but not directly join, until this past week, European negotiations with Iran. As recently as April, Bush was still publicly wedded to this logic.

"With the United States being the sole interlocutor between Iran, it makes it more difficult to achieve the objective of having the Iranians give up their nuclear weapons ambitions,'' Bush said in answering questions following an April 10 speech. "It's amazing that when we're in a bilateral position, or kind of just negotiating one on one, somehow the world ends up turning the tables on us.''

Arguably, however, the opposite has been true. In the case of Iran, the Europeans, including Great Britain, have consistently urged the United States to talk directly to Iran.

An excuse not to talk

All the other partners in the six-party talks, including the closest U.S. ally, Japan, have held their own direct talks with Pyongyang and pushed the United States to do the same. Ultimately, it is the United States that has found itself isolated.

North Korean experts in the State Department had warned against relying only on this approach.

"In the case of negotiating with North Korea, more is not merrier and certainly not more efficient,'' says Robert Carlin, a longtime CIA and State Department intelligence expert on North Korea who participated in virtually all negotiations with the North from 1993-2000. "The more parties and people at the table, the greater the likelihood of posturing, and the harder it is to make concessions.''

In his view, the insistence on a multilateral approach was initially an excuse not to talk. "They didn't want bilateral talks with Pyongyang and they certainly didn't trust the State Department to conduct any such thing.''

These divisions have persisted. Last September, with the backing of Secretary of State Condoleezza Rice, the State Department's chief negotiator was finally allowed to meet his North Korean counterpart. This led to an agreement in the six-party talks last September, a compromise that conceded in principle the North Korean right to have a nuclear power reactor.

That deal prompted a backlash from Cheney and others, according to senior officials within the administration, and fresh curbs on direct contacts with Pyongyang. But the new proposal to Iran apparently also includes an offer to supply power reactors.

What still has resonance is the belief that direct talks with North Korea and Iran amount to acceptance of the regimes in power in both countries.

Resistant to deal

"Ultimately the president is, on this issue, very, very resistant to the idea of doing a deal, even a deal that would solve the nuclear problem,'' Flynt Leverett, who dealt with Iran for the Bush National Security Council, said in a recent interview. "You don't do a deal that would effectively legitimate this regime that he considers fundamentally illegitimate.''

The administration may calculate that this offer of talks will only serve to isolate Iran and shore up ties with Europe. But it may have stepped onto a slippery slope toward a bargain that will necessarily involve painful concessions to Iran and lead toward a resumption of diplomatic relations broken off almost three decades ago.

Opposition to negotiating with the enemy is deeply embedded in the Bush administration. There is, however, a precedent for a sea change -- Ronald Reagan. President Reagan came to office in the wake of the Soviet invasion of Afghanistan and the American boycott of the 1980 Moscow Olympics. Dialogue with the Soviets was halted and the staff of the Reagan National Security Council opposed any contacts with Moscow.

Reagan himself, in a famous 1983 speech, referred to the Soviet Union as an ``evil empire,'' followed two weeks later by the launching of the "star wars'' missile-defense program. Soviet leaders, we learned later, were convinced that the United States might launch a first strike. In August of that year, Soviet fighter aircraft shot down a Korean Airlines passenger jet that had strayed from its flight path, a sign of sharply increasing tension.

In the Reagan administration, against fierce internal opposition, Secretary of State George Shultz pushed to resume dialogue with the Soviets, beginning with achievable steps such as resuming grain sales. Reagan ultimately agreed, starting down a road that led to the series of dramatic summits from 1985 with incoming Soviet leader Mikhail Gorbachev.

Reagan's willingness to sit down with the "evil'' foe flowed from a sense of conviction in American strength. It is not yet evident that his Republican successor shares the same sense of confidence.