A much-touted two-day summit between Donald Trump and North Korean leader Kim Jong-Un failed to reach the finish line Thursday, as talks collapsed and Trump returned to Washington, DC. It’s unclear exactly what unraveled the process; Trump says Kim asked for the lifting of all economic sanctions in exchange for closing the Yongbyon Nuclear Scientific Research Complex, while North Korea reportedly says it had asked for relief on some, but not all. But throwing around blame for Hanoi misses the point: The summit was a mistake to begin with.

That’s not to say the US and North Korea shouldn’t pursue negotiations over the Hermit Kingdom’s nuclear disposition. They absolutely should, and will continue to, per Trump’s departing remarks. “Chairman Kim and myself, we want to do the right deal,” Trump said. “Speed is not important.” But within that otherwise upbeat assessment lies the main impediment to real progress in the Korean Peninsula: Trump and Kim should not be the ones doing the deal, at least not the bulk of it. Hanoi is what happens when they try.

Trump has built his brand as a master negotiator, despite uneven results in the political realm. And in fairness, his gambit to meet with Kim in Singapore last summer resulted at the very least in what international relations wonks call confidence-building measures. Importantly, North Korea hasn’t tested a ballistic missile or nuclear weapon in over a year. And its relationship with South Korea, while still tense, has somewhat thawed.

“These are positive steps, and show that the North Koreans are at least willing to have negotiations, and engage in diplomacy with South Korea and the United States,” says James McKeon, a policy analyst at the Center for Arms Control and Non-Proliferation, a DC-based nonprofit.

But in the months since Singapore, North Korea has offered little to no evidence of curtailing its weapons programs. And why would they? Despite Trump’s declaration last June that “there is no longer a Nuclear Threat from North Korea,” the Singapore accord affirmed only that “the DPRK commits to work toward complete denuclearization.” They’ll get to it, eventually, at some point, or at the very least give it some serious thought.

Chalk the vague language, and the resulting lack of verifiable progress, up to Trump’s untraditional diplomacy. ”When we first were looking at this going into the Singapore summit, we were saying that it was ass backwards. This is not the way you’re supposed to do it,” said former ambassador Robert Gallucci in a call with reporters. “You don’t start with the summit. You finish with the summit, and you make sure all the prep work is done, and then the two big guys presumably come together and sign something.”

Gallucci would know; as chief US negotiator, he helped secure the 1994 Agreed Framework, which tamped down North Korea’s nuclear ambitions for nearly a decade. And while he acknowledges that tensions between Kim and Trump may have escalated to such a dangerous point last summer—thanks in no small part to Trump’s own rhetoric—that a shotgun summit in Singapore was needed, he and others argue that it’s not a viable process for substantive change.

“President Trump’s unorthodox approach to diplomacy has created an opening, starting back in Singapore and continuing to Hanoi,” says Lynn Rusten, who served as senior director for arms control and nonproliferation in the Obama administration and currently works on nuclear issues at the nonprofit Nuclear Threat Initiative. “But the only way that they can capitalize on that and bring it to fruition is to revert now to the more traditional negotiating process.”

Hanoi was anything but. Trump appointed the widely respected Stephen Biegun as special envoy to North Korea six months ago, but Biegun has only been able to conduct a single round of working-level talks with his North Korean counterparts. And even that came only in the last three weeks, after Trump announced when the summit would take place during his State of the Union address.

Nuclear diplomacy is not American Ninja Warrior. You don’t get bonus points for navigating obstacles faster. “It’s completely unrealistic to think that you can just go in with very little preparation and reach an agreement on something that is so complex,” says Rusten, especially given how enmeshed the nuclear issues are with a broader set of regional economic and security concerns. “There’s got to be an incremental, step by step approach.”

That should be especially evident given North Korea’s long history of failing to keep its nuclear promises. As much as Trump has touted denuclearization as the endgame, arms control experts widely agree that there’s likely no way to get there overnight, or in a single sit-down. What it will take is weeks or months or more of people on the ground hammering out fine details, not a single two-hour meeting between two heads of state. Especially when at least one of them likely has other things on his mind.

And while Thursday’s failure could have been worse—Trump could have, say, promised to withdraw all US troops from South Korea, or Kim could have threatened to resume missile testing—it extracts a real cost. By trying for a grand bargain, Trump and Kim missed the opportunity to establish clear, specific goals that their teams could work then work towards.

“It’s somewhat surprising that they would play such high-stakes poker at such a high-profile event,” says Jenny Town, analyst at North Korea watchdog 38 North. “It’s really hard to see how we might maintain momentum going forward.”

Maintaining the status quo is preferable to more nuclear tests, but it’s not a viable long-term solution. “While it’s good that tensions are down, North Korea is continuing to churn out fissile material and produce weapons,” says Rusten. “The facts on the ground continue to change in a negative direction.”

It’s admirable that Trump has made neutralizing the threat from North Korea a top priority. The relative calm of the last eight months shouldn’t be dismissed. But if the White House wants to make actual progress, it needs to put in the work before the next high-profile meeting. That’s one concession Trump, so far, seems unwilling to make.

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