No progress has been made in denuclearization negotiations since U.S. President Donald Trump and North Korean leader Kim Jong Un held their historic first face-to-face meeting in Singapore last year. Worse still, since May Pyongyang has resumed provocative short-range ballistic missile launches that violate United Nations Security Council resolutions and threaten the security of Japan and South Korea. Relations between the United States and North Korea appear to be returning to the confrontation it was in 2017.

In 2018, North Korea suspended nuclear and missile tests and the United States halted joint military drills with Soth Korea. These double suspensions provided conditions for dialogue. However, this formula has collapsed. Trump said that Kim had lived up to his pledge to halt long-range missile tests. Then, this month, North Korea claimed that it conducted a “very important test” twice, signaling it could be ready to launch an intercontinental ballistic missile at any time.

Kim warned that Dec. 31 is the deadline for a new proposal from Washington. North Korea has put the U.S. on notice that it will face a “greater threat” if it ignores this deadline. Kim, in his 2019 New Year’s speech, already warned that North Korea would be “compelled to explore a new path” if the U.S. “seeks to force something upon us unilaterally … and remains unchanged in its sanctions and pressure.”

Is Kim’s provocative posture a bluff or for real?

As the deadline and presidential election year approaches, it appears uncertain if Trump can maintain the status quo on the Korean Peninsula, which seems stable compared with 2017’s “fire and fury.”

Apparently Kim is frustrated by the U.S. stance and wonders how far he can go on a new path. On the other hand, Trump’s all-or-nothing deal has stalled. What Kim and Trump are facing are mutual warnings — namely, Kim’s Dec. 31 deadline and Trump’s red line of a nuclear weapon test and ICBM launch.

In the midst of growing uncertainty, there are three possible scenarios for before and after the Kim’s deadline.

Scenario A is the status quo. The current situation is acceptable for Trump, who is seeking re-election next year and has repeatedly pointed to the current relatively stable situation of the Korean Peninsula as a major diplomatic achievement. Kim also might carefully limit his “new path” so as to not cross Trump’s red line.

Scenario B is a worst-case scenario in which North Korea’s provocations cross the red line.

Kim might feel domestic pressure as his diplomacy has made no progress toward lifting sanctions since the breakdown of the second summit in Vietnam in February. He must be tough.

Trump, in response, would have no choice but to return to the “maximum pressure” strategy that he abandoned after the summit in Singapore. Under this scenario, once the Korean Peninsula returns to the 2017 crisis, it would be difficult to repeat the “fall-in-love” diplomacy in which they engaged in 2018. Tensions would grow and lead to a confrontation that risks a military conflict.

Scenario C is a risky scenario in which Trump changes the U.S. negotiating position and makes a partial deal with Kim.

Trump and Kim can no longer enrapture one another, nor convince the world of their determination to achieve denuclearization through a vague and ambiguous political deal like the one they made at the 2018 Singapore summit. At the same time, it is almost impossible to reach an agreement on complete denuclearization based on the Libya model in which the U.S. lifts sanctions only after the complete dismantlement of North Korea’s nuclear capabilities, because that would remind him of the end of the Gadhafi dictatorship and make him suspect that a future U.S. administration will pursue regime change after North Korea gives up its nuclear arsenal.

Some say that a partial deal is a bad deal and that no deal would be a better choice. However, not reaching a deal would create significant uncertainty and danger, including countenancing Pyongyang’s continuous development of more sophisticated nuclear weapons and missiles in an effort to become a de facto nuclear power.

On the other hand, if a partial deal is made at the beginning of a sequence of several stages leading to complete denuclearization, it would not necessarily be a bad one. A Stanford University research institute report concluded that a gradual approach starting with the most dangerous part of North Korean’s nuclear capabilities would be the best approach, as the denuclearization process would take at least 15 years. It is important to avoid the same failures that marked past negotiations and agreements by defining the scope and sequence of the measures taken by both sides in a step-by-step approach toward denuclearization and the foundation of a peaceful North Korea regime.

The negotiations, however, are difficult because the measures to be traded between the two sides are asymmetric. They are more complicated than symmetric nuclear disarmament negotiations, such as those held on the Intermediate-Range Nuclear Forces Treaty, which eliminated 2,682 missiles by 1991 followed by 10 years of on-site verification inspections by both sides.

More than that, any positive response toward the foundation of a peaceful regime in North Korea would have a tremendous impact on the security environment in East Asia. In addition, Trump has demanded Seoul to pay 400 percent more in 2020 for hosting 28,500 U.S. troops in South Korea. If Trump is not satisfied by Seoul’s response and orders even a partial troop withdrawal from South Korea to please his political base ahead of the presidential election, the security implications would be significant. It could weaken U.S.-Japan-South Korea defenses against North Korea and undermine the U.S. allies’ trust in Washington’s security assurances.

Therefore, any partial deal should be designed very carefully. It would be important to start from the most difficult part of denuclearization and be verified through international inspections.

U.S. President Ronald Reagan, who signed the INF Treaty with Soviet leader Mikhail Gorbachev, said, “Trust, but verify.” In effect, anyone might doubt Kim is prepared to give up his nuclear weapons and missiles, which have been developed at great cost, increase North Korea’s security and status internationally, and maintain the military’s loyalty domestically. North Korea’s poor track record may also remind policymakers in the U.S. and Japan of its noncompliance with the deals that have been made.

Verification is an indispensable element in the step-by-step denuclearization of North Korea. If it is incorporated in the deal with a road map toward complete denuclearization, a gradual and simultaneous approach is worth trying. The next U.S. president may say, “Agree, but verify.”

Masahiro Kohara is a professor at the University of Tokyo’s Graduate School of Law and Politics. Previously he served as a career diplomat in the Foreign Ministry.