On Tuesday, Deputy Secretary of State John Sullivan said of North Korea that the current U.S. “focus is on diplomacy to solve this problem that is presented by the DPRK. We must, however…be prepared for the worst, should diplomacy fail.” Not surprisingly, most recent commentary and analysis on the current North Korea crisis has focused on the prospects of either a near-term conflict or a diplomatic way out. That focus is understandable, but fixates on the two least likely outcomes. Rather than preparing for diplomatic or warfighting scenarios with a nuclear-armed North Korea, the United States should be preparing for a sustained period of deterrence, coercive diplomacy, and rollback. This is the best approach to achieve the international community’s long-stated goal of the eventual peaceful denuclearization and reunification of the Korean Peninsula at an acceptable cost.

Until now, every previous North Korean nuclear crisis somehow seemed to end with a new diplomatic framework for disarmament of the peninsula. We can be quite sure that will not be the scenario this time. Pyongyang now has a perfect record for destroying all previous agreements aimed at curbing its nuclear weapons ambitions — from the first North-South agreement banning nuclear weapons on the peninsula in 1991, to the Clinton administration’s 1994 Agreed Framework, the 2005 Six Party Joint Declaration of the George W. Bush administration, through the Obama administration’s “Leap Year” deal in 2012. Lest there be any residual doubt about Pyongyang’s intentions, the North Korean Constitution was changed in 2012 to codify the country’s nuclear weapons status. Pyongyang has also rejected all Chinese, Russian and South Korean overtures to discuss nuclear disarmament in the current cycle of crisis.

Even with increased sanctions and military pressure — which we think are necessary for other reasons, to be outlined below — the North is unlikely to change its basic stance on retention of nuclear weapons any time soon. At most, the United States might be able to negotiate a “freeze-for-freeze” arrangement as proposed by Beijing and Moscow, which would see Pyongyang stop nuclear and ICBM tests in exchange for a U.S. halt to regular military exercises and missile defense deployments. There are numerous problems with the “freeze-for-freeze” idea. To begin with, it confers legitimacy on the North’s nuclear weapons tests. North Korea is an illegal nuclear state, though there is nothing illegal about military exercises and missile defense. Moreover, it would undermine Japanese and South Korean confidence by leaving in place existing nuclear weapons and shorter-range missiles ranging those countries. And finally, a freeze-for-freeze would stop necessary and legitimate upgrades to U.S. and allied deterrence capabilities without any material reduction to the North Korean nuclear and missile threat.

We can also rule out the alternate option being floated by some — a preventive military strike against North Korean nuclear weapons and missile facilities. While there may be leverage to be gained from demonstrating a willingness to consider that option, the consequences of actually acting would not be worth the costs of intentionally starting a war. A U.S. attack would be unlikely to eliminate all of the North’s missile and nuclear capabilities, and would likely invite a North Korean military response. Though retaliation from Pyongyang would result in the destruction of the North Korean regime, it could also cause over a million casualties in South Korea and Japan, not to mention the danger of North Korean transfer of nuclear weapons to terrorist groups hostile to the United States. The odds that the North would respond with its full capabilities are probably below 50% given the potential consequences to the regime, but the risk-benefit analysis still does not result in acceptable terms for the United States.

Deterrence and gradual rollback of the North Korean threat is therefore the best, and indeed, only option going forward. However, it is important to recognize that this approach would be significantly different from U.S. containment and deterrence of the Soviet nuclear threat during the Cold War for several reasons.

First, and most importantly, the United States and the international community do not accept North Korea as a legitimate nuclear-armed state and the United States should retain its longstanding declaratory policy of aiming for the denuclearization and reunification of the Korean Peninsula. Some argue that we should officially accept the reality of North Korea’s nuclear weapons, but this would risk legitimizing the nuclear program and setting a precedent that would weaken the global nonproliferation regime. Moreover, one can simultaneously refuse to recognize North Korea’s nuclear weapons while still planning for a serious deterrence policy as we outline below.

Second, the Soviet Union was a peer competitor, but the United States enjoys clear superiority over North Korea on every dimension of power and has many more options for thwarting and eventually rolling back the threat. These advantages include military escalation dominance, economic power to bring crippling sanctions to bear, and capable regional allies also seriously committed to denuclearization. To be sure, China’s halting support for North Korea complicates this calculation, but, even with Beijing’s help, North Korea is not the Soviet Union.

Third, while the Soviet Union had hegemonic and irredentist ambitions, over time, it became interested in a more stable strategic relationship with the United States. North Korea has no such interest. Rather than seeking nuclear stability as the Soviets did, North Korea will seek continued terror and instability in order to demand concessions that keep the regime afloat, possibly including efforts to decouple the United States from South Korea in order to keep open the option of forceful absorption of the South (a long shot, but indispensable to the Kim regime‘s raison d‘etre).

North Korea made its demands clear to U.S. negotiators in Pyongyang in October 2002: an end to the U.S. nuclear umbrella over Japan and Korea, the withdrawal of U.S. forces from both countries, and economic aid to the regime. We can expect that the North, armed with what it believes to be impunity provided by nuclear weapons, will take actions that terrorize without inviting complete destruction of the regime. These steps may include exploding nuclear devices in the Pacific Ocean, or in space (though it may not quite yet have the capability) to take out satellites or to generate an electromagnetic pulse; conducting cyber-attacks; initiating submarine attacks against South Korean ships; firing missile shots closer to the Japanese homeland; or once again transferring nuclear-related technologies to hostile third parties, similar to the regime’s assistance with Syria’s el Kibar nuclear reactor. And, although unlikely, future crises with a nuclear-armed North Korea will carry some inherent risk of nuclear war. The dynamics of deterrence will inevitably be more demanding, if less globally threatening, than those with the Soviets. Simply learning to live with a nuclear-armed North Korea and attempting to deter and contain it, therefore, is not an option.

For all of the above reasons, we believe the administration should be preparing with allies for a new strategy that combines coercive diplomacy, defense and deterrence, and reassurance of allies with the long-term goal of disarming and reunifying the Peninsula.

The most important element of coercive diplomacy for the coming few years will be the coercive part, not the diplomatic part. The administration needs to put in place a regime of economic sanctions that will not be reversed at the earliest sign of diplomatic engagement from North Korea, a mistake constantly made in Washington over the previous two decades. Many mistakenly believe North Korea is one of the most sanctioned countries on Earth, but, in reality, Washington is just getting started. The Treasury Department has ample room to turn up the heat, especially through so-called secondary sanctions. The Trump administration’s Sept. 21 executive order was an excellent and overdue step that goes well beyond past and existing sanctions measures. The new sanctions will be the first to target all North Korean nationals and, importantly, the first that delegates to the Treasury Department the authority to go after any foreign bank doing business with North Korea, including banks in China that prop up or finance the regime. It is noteworthy that Beijing began reigning in its banks only after the United States imposed these unilateral sanctions.

Backed by intelligence and diplomatic resources, these new authorities could force every economic entity on Earth to choose between doing business with North Korea and doing business with the United States. The sanctions will also help to reinforce a net against outward proliferation, making it more difficult for Pyongyang to transfer nuclear and missile technology to other hostile regimes like Iran or Syria.

Talking to North Korea now only makes sense if the engagements are designed for clear messaging and intelligence collection and not invested with the expectation of real diplomatic progress. In the coming months and years, tough and consistent sanctions will further cripple North Korea’s economy. This could hasten the collapse of the Kim regime, or force it, fearing this outcome, to come to the table to talk denuclearization in earnest.

The second element of our proposed approach is a serious defense and deterrence strategy to address the threat that exists here and now. This strategy requires a defensive and offensive component. On the defensive side, the United States should strengthen homeland ballistic missile defenses. This could include building an East Coast site, increasing the number and sophistication of ground-based interceptors, and investing in next-generation technologies, such as boost-phase lasers. The United States could encourage South Korea to purchase shorter-range systems from Israel, such as Iron Dome, to help defend against North Korean artillery. Additional U.S. THAAD batteries and Aegis ship deployments to the region may also be necessary. Military pressure can also be applied by cyber and “left of launch” attacks to impede the development of North Korea’s missile program.

To be sure, missile defenses do not provide a perfect defense, but even critics acknowledge that they provide limited protection against regional powers, like North Korea, which contributes to both defense and deterrence.

On the offensive side, as the administration has stressed repeatedly, the United States must have credible military options. Even if a preventive strike is not on the table, if North Korea is on the verge of launching an attack, the United States must at least retain the option of preempting it. And, of course, if North Korea uses a nuclear weapon, we must prevent it from using a second or a third. This means the United States needs the ability to find, fix, and finish North Korea’s nuclear and missile program. This might require improved intelligence, surveillance, and reconnaissance over North Korea. It might also require improved offensive strike capabilities, including a more flexible nuclear force. The United States has repeatedly stated that a North Korean nuclear attack would result in the end of the Kim regime, so to be credible, the United States and South Korea must also maintain and continually update plans to execute this threat should deterrence fail.

The Trump administration must also take steps to make the military element of the strategy credible. This begins with clear messaging. The administration’s rhetoric may create more hype than is helpful (we prefer a Theodore Roosevelt approach of speaking softly and carrying a big stick) but a willingness to use force is absolutely necessary. Contrary to some recent hysteria, we do not worry that verbal escalation alone will lead to war (international relations theory actually suggests the opposite). The deployment of strategic assets such as B-1s and B-2s to new locations in the region, and at a heightened frequency, is one important demonstration of willingness and readiness for all military options in the face of North Korean intimidation or attack. Such shows of force deter not just nuclear weapons use, but also other provocations the regime may explore.

Some worry that a strengthened U.S. deterrence strategy could provoke North Korea to strike first, but, to the contrary, these steps are essential to deterring Pyongyang and reassuring regional partners. It is not logical that Kim Jong Un, fearing a nuclear war with the United States, would intentionally initiate nuclear war against the United States.

The third component is greater reassurance for allies and strengthening of alliances. The U.S. alliance network in East Asia consists of a “hub and spokes” of separate bilateral treaties designed after the Korean War. These alliances must move in the direction of collective security to deal with the common threat. This is critical for four reasons. First, in contrast to the past, today Japan is on the front lines, threatened directly by North Korean missiles and nuclear weapons, not to mention cyber and other threats.

Second, strengthening trilateral defense cooperation is also more possible now than in decades before. While political ties between Japan and South Korea remain challenging, the two militaries are on good terms and recognize the need for more seamless coordination of planning and logistics. It did not help that the president criticized South Korean President Moon Jae-in and threatened to leave the U.S.-Korea free trade agreement (KORUS) in the midst of the crisis with North Korea in early September, though the adversarial approach towards Seoul appears to have diminished.

Third, movement towards a regional collective security arrangement would put pressure on China to rethink aid to North Korea. Beijing, which provides over 80 percent of the Kim regime’s fuel and food, is clearly in a position to do more, but will not do so for strategic reasons. China’s grand strategy is clearly premised on the assumption that U.S. bilateral alliances will atrophy as Beijing’s economic and diplomatic clout grows in the region. But if the United States and its allies strengthen missile defense and other cooperation, it will put pressure on Beijing to do more about the North Korean problem. By taking legitimate steps to strengthen mutual defense, the United States and its allies have the opportunity to change Chinese strategic calculations.

Finally, if the United States does not lead with a more assertive alliance posture that includes Japan and South Korea, then each of those allies will hedge against the North Korean threat on their own, which will exacerbate Japanese-South Korean tensions and weaken U.S. leverage towards both China and North Korea.

To maintain the initiative, the United States should seek a collective security statement with Japan and South Korea that an attack by North Korea against any one of these three countries would constitute an attack on all. In fact, the three came close to issuing such a statement in December 2010. Circumstances are far more serious today. The United States should stand up a permanent missile defense task force with U.S., Japanese, and South Korean AEGIS ships, building on the trilateral “Pacific Dragon” missile defense exercises the countries started on the margins of the RIMPAC exercises last year.

Some in South Korea are calling for a return of U.S. tactical nuclear weapons to the Korean peninsula, but this is unnecessary at this point. Instead, the United States should increase the credibility of its extended nuclear deterrent in Asia. The Obama administration promised that U.S. tactical nuclear weapons would be “deployable” to Asia. The Trump administration can make good on this promise by refurbishing nuclear weapons storage areas in Asia and more regularly exercising nuclear-capable fighter aircraft in the region. In addition, the United States could re-introduce more flexible tactical nuclear options, such as the TLAM-N submarine-launched nuclear cruise missile. The Obama administration retired this capability much to the dismay of Asian allies, and bringing it back would go a long way toward strengthening extended deterrence and assurance. Critics might fear that these steps could increase the risks of escalation, but, in fact, they will provide clear evidence of U.S. capability and intent to extend deterrence to Asia and reduce the chances of miscalculation.

China will have to play a key role, but we must recognize that Beijing will be more forthcoming when it recognizes Washington’s ability to set the strategic terms. The administration will have to keep an open attitude towards strategic cooperation with China on the North Korea problem, but is far more likely to win Beijing’s cooperation when it is clear that the United States and its allies will not remain passive in response to the mounting North Korean threat. Appealing to Beijing’s self-interest in a denuclearized Korean peninsula has proven far less effective than demonstrating U.S. intentions to take action.

In the end, this strategy does not guarantee success, but it is the best among bad options. The repeated cycle of crisis and then outside aid to Pyongyang since the end of the Cold War has only resulted in a more dangerous North Korea. Our proposed strategy breaks that cycle and increases pressure on the Kim regime to move towards serious diplomacy over the medium-to-long term. However, given the regime’s unmistakable rejection of denuclearization, diplomacy will have to take a back seat while real pressure, defense and deterrence are restored. It must be clear that the pressure on Pyongyang will continue to increase so long as it stays on its current path. The North must also know that the U.S. response to a large-scale attack will be effective and overwhelming, and that provocations and attacks below the threshold of war or breaking the armistice will be met with a strong and proportional response. North Korea’s nuclear weapons will not deter the United States and South Korea from responding. U.S. policy must ensure that the North Korean leadership receives none of the benefits of nuclear weapons it has sought in terms of legitimacy, economic aid, or a weakening of the U.S. commitment to South Korea and Japan. This strategy will test the patience and willpower of the United States and its allies, but it is the only plausible strategy if we are to prevent war and, eventually, achieve peaceful denuclearization and reunification of the Korean peninsula.

Michael J. Green is Chair in Modern and Contemporary Japanese Politics and Foreign Policy at Georgetown University and Vice President for Asia at the Center for Strategic and International Studies (CSIS). He previously served as Special Assistant to the President and Senior Director for Asian Affairs on the NSC staff of President George W. Bush.

Matthew Kroenig is Associate Professor of Government and Foreign Service at Georgetown University and a Senior Fellow in the Brent Scowcroft Center on International Security at the Atlantic Council. He formerly served as a strategist in the U.S. Department of Defense and he is the author of The Logic of American Nuclear Strategy (Oxford University Press, forthcoming 2018).

Image: U.S. Army/Capt. John DePinto