The June 12 summit between Donald Trump and Kim Jong Un in Singapore seems back on the calendar. But it’s not likely to result in the peaceful denuclearization of the Korean Peninsula.

Why not? The answer comes down to trust: The United States and North Korea would be foolish to trust any promises the other side makes in Singapore. Without a minimum of trust, any deal would be either cosmetic, incomplete or doomed to fail. Here’s why.

The U.S. and North Korea have a long history of distrust

The United States and North Korea have fundamentally incompatible interests. Kim and his regime want to retain power. To do so they need to maintain a closed, rigidly oppressive regime, with minimal contact with and ideological contamination from the much more prosperous South Korea. North Korea also believes that nuclear weapons are essential to the regime’s survival — and to warding off threats from the South and from the United States.

TheUnited States, for humanitarian and strategic reasons, would prefer to see the North Korean regime collapse, and have South Korea take over a unified Korean Peninsula. The American aim, largely unchanged since the initial division of Korea in 1945, thus is fundamentally at odds with North Korea’s primary goal.

Why does North Korea hate the U.S.? Look to the Korean War. (Anna Fifield, Jason Aldag/The Washington Post)

But can’t summits overcome mistrust?

Scholars of diplomacy have argued that leaders can build trust via face-to-face interactions at summits. The remarkable turnaround in U.S.-Soviet relations under Ronald Reagan and Mikhail Gorbachev is an example — over the course of five summit meetings, the two leaders ended the Cold War and transformed world politics.

But summits only work if the leaders are trustworthy, or at least have incentives to be so. Gorbachev wanted to end the Cold War for a mix of practical and ideological reasons. The Soviet Union was unable to keep up with the United States and Gorbachev had lost faith in communist ideology. He had good reason to be a trustworthy partner for Reagan in arms control agreements, and the United States also had an incentive to limit strategic competition.

When leaders are untrustworthy, summits fall short. When British Prime Minister Neville Chamberlain met German Chancellor Adolf Hitler at Munich in 1938, no trust was built, and Hitler tossed aside the agreement later that year and proceeded to conquer the rest of Czechoslovakia. Even with less duplicitous leaders, summits can be useful to manage normal relationships, but they rarely transform them from enmity to friendship.

Can the U.S. and North Korea trust each other?

If summits can only build trust between the trustworthy, a U.S.-North Korean summit is probably not destined for success. Both countries have structural reasons to be untrustworthy — the Kim regime wants to keep its nuclear weapons and retain power, and Washington wants Pyongyang to give them up and fall.

As a result, North Korea has behaved in a quintessentially untrustworthy fashion over the years, offering sham concessions when the pressure is on, all the while secretly forging ahead with its nuclear and missile programs. For its part, if the United States thought that a conventional military intervention such as the one that overthrew Moammar Gaddafi in Libya would topple the North Korean regime at an acceptable cost, it could very well do it.

Trump and Kim are untrustworthy

But what about these two leaders, Trump and Kim — could they redefine state interests and cooperate if they build a personal relationship of trust? Trump and Kim are poor candidates for such a role. Kim ordered his own uncle and half brother killed out of fear that they might conspire against him.

Kim rules a totalitarian regime with a cult of personality. Personal integrity toward the United States — or any foreign nation — is probably not high on his list of values. He will almost certainly attempt to cheat on any deal he might negotiate with Trump, hiding components of the nuclear program until times change and he feels safe to return to a confrontational stance.

Trump’s history of conflicting statements and tweets might give reason to doubt his  credibility. But one of Trump’s long-held beliefs suggests he might appear more trustworthy to North Korea than previous U.S. presidents. Trump has often declared that alliances are a sucker’s game for the United States — and that allies, in his view, act as freeloaders.

Trump would probably be quite willing to trade away the U.S. presence in South Korea for a non-nuclear North Korea. This kind of concession might at least marginally increase the credibility of a U.S. promise to leave a non-nuclear North Korea alone.

But even without U.S. troops in South Korea, Trump could still intervene with air assets from Japan or further afield. And Trump’s successor might decide to renege on the deal and move troops back to South Korea. Trump has blazed that trail by reneging on the Iran nuclear deal negotiated by his predecessor, Barack Obama. In an era of partisan polarization, U.S. promises are less binding than they were.

But aren’t threats enough?

Why care about trust, anyway? Isn’t international politics really all about threats and coercion? And isn’t North Korea’s recent change in behavior due to Trump’s threats rather than his promises? Trump probably does have a more credible threat to use force against North Korea than his predecessors, for a variety of reasons.

However, successful coercive diplomacy requires both credible threats (if you build nuclear weapons I will attack) and credible promises (if you don’t I will leave you alone.) If Kim thinks the United States will attack him with or without nuclear weapons, he certainly has no incentive to disarm.

Threats may have persuaded Kim to tack toward conciliation once more, as his father and grandfather did on occasion. But without credible promises, threats alone are no more likely to secure a denuclearized North Korea now than in the past.

Andrew Kydd is a professor in the University of Wisconsin’s department of political science.