“Sometimes you just have to walk.”

That was how U.S. President Donald Trump explained the stunning breakdown in nuclear talks between him and North Korean leader Kim Jong Un in Hanoi on Thursday.

Trump told a hastily organized news conference in the Vietnamese capital that while the talks had faltered, “we had a really, I think, productive time.”

He said the talks at the second summit, some eight months since the two leaders’ landmark first meeting in Singapore, had been derailed over the U.S. side’s refusal to completely ease crushing U.N. and unilateral sanctions.

“It was about the sanctions,” Trump said. “Basically they wanted the sanctions lifted in their entirety, and we couldn’t do that.”

The revelation came after the two sides earlier cut short their summit, including a planned lunch and “joint signing ceremony.”

Trump attempted to put an optimistic shine on the rift, noting that the two sides had parted ways amicably and revealing that Kim had vowed “no testing of rockets or missiles or anything having to do with nuclear.”

The North’s last nuclear test, in September 2017, was also its sixth and largest. Its last ballistic missile test was in November that year, when it tested a long-range missile that experts say is capable of striking much, if not all, of the continental United States.

But Secretary of State Mike Pompeo said that Washington asked Kim “to do more. He was unprepared to do that.” Pompeo also noted that “timing and sequencing issues” had failed to meet the expectations of U.S. negotiators.

“We just felt it wasn’t appropriate to sign an agreement today,” Trump said. Neither Trump nor Pompeo noted what exactly Kim had refused to do, but the president indicated the North Korean leader wouldn’t agree to proceed as far toward abandoning his nuclear program as the U.S. demanded in exchange for sanctions relief.

In Tokyo, Prime Minister Shinzo Abe praised Trump after the news for “not striking an easy compromise” on the denuclearization issue.

“With a strong determination to realize denuclearization, (Trump) didn’t strike an easy compromise,” Abe told reporters after a telephone conversation with the U.S. president. “I support Mr. Trump’s decision.”

The prime minister also said Trump had explained Abe’s stance on the issue of Japanese nationals abducted by North Korean agents during the one-on-one meeting with Kim.

“Next, I myself must face chairman Kim Jong Un” to resolve issues related to Japan, he said.

Abe has made addressing the issue of Japanese nationals kidnapped by North Korean agents in the 1970s and 1980s one of his administration’s top priorities.

Despite the talks’ breakdown, some analysts said Tokyo “will not be unhappy with this outcome.”

“While sanguine publicly, the Abe government would have been worried about the prospect of Trump cutting a side deal with Kim that limited threats to the continental U.S. … but not those to Japan in the form of Nodong delivery systems,” Andrew O’Neil, an expert on North Korea and a professor at Griffith University in Australia, said in reference to intercontinental ballistic missiles and shorter-range Nodong weapons that Tokyo views as a top threat.

At his news conference, the U.S. leader also said Kim had offered to dismantle North Korea’s Yongbyon nuclear facility, but “it wasn’t enough.” Pompeo said even without Yongbyon, the country would still possess missiles, warheads and other elements of a nuclear program that were unacceptable to Washington.

“I want to take off the sanctions so badly because I want that country to grow,” Trump said. “But they had to give up more.”

Van Jackson, a former Pentagon official and North Korea expert, characterized the talks — and the spectacle surrounding them — as “a reality show.”

“This is the dramatization of diplomacy in a way that sabotages real diplomacy,” said Jackson, who currently teaches at Victoria University of Wellington in New Zealand. “What is there to say. Yes, Yongbyon would’ve been a stepping stone but a costless signal. But we can’t trust Trump is giving it to us straight; he’s a proven liar, so we can’t take what he says at face value.”

Jackson also noted that the North Koreans were not being upfront in their concessions, having previously shut down Yongbyon in 2008, “and less than a year later they tested a nuke.”

“The threat potential from North Korea comes from their stockpile of warheads, missiles and launchers,” he said. “That’s what needs to be addressed.”

Shutting down Yongbyon again, he said, would not have been “in any way evidence that they’re on the path to denuclearization.”

The president also acknowledged publicly that the U.S. was aware of more than one nuclear fuel enrichment site across the country, something he said had surprised the North Koreans.

Dismantling those sites — or at least acknowledging their existence — was likely high on the White House’s wish list.

Malcolm Davis, a senior defense analyst at the Australian Strategic Policy Institute think tank in Canberra, said the sites’ existence meant the North could dismantle Yongbyon and still continue to develop its nuclear capabilities with impunity.

Speculation had grown in recent weeks that the two sides would agree on a nonbinding declaration ending the 1950-53 Korean War, which was halted only with an armistice, as well as setting up liaison offices, diplomatic posts that are more limited than embassies. Both moves would have marked a large step in normalizing ties.

But the declaration, although symbolic, could have been spun by Trump as a major foreign policy victory as he faces mounting pressure at home over investigations into Russian meddling in the election.

Trump now returns to Washington just a day after the president’s former personal lawyer, Michael Cohen, described him as a “racist,” a “con man,” and a “cheat” — though he had told the truth when he said there had been “no collusion” with Russia — in bombshell testimony before Congress.

Victoria University of Wellington’s Jackson said that Trump was “clearly distracted by what’s going on with Cohen” during the negotiations.

“We could have President Pence by the end of the year, and Trump knows it,” he said, referring to Vice President Mike Pence. “If that’s your mindset, who cares about diplomacy with Kim Jong Un, especially when Kim wants sanctions relief that you probably can’t give.”

As for the possibility of future talks, Trump did not rule out that they could happen, but noted pointedly that there was no timeline. Still, he said the summit had ended amicably with a handshake before the two leaders departed.

“There’s a warmth that we have,” Trump said, adding that the two sides were “positioned to do something very special.”

Pompeo also attempted to put a positive spin on the events, saying “the departure was with an agreement” that the two sides would continue negotiations, and that they are “closer” to an eventual deal.

Earlier in the day, Trump had touted his discussions with Kim, stressing that he was in “no rush” to push the North to relinquish its nuclear weapons program and emphasizing that his administration had switched tack from demanding the North quickly give up its nukes to taking a “longer-term” approach.

“Speed is not very important to me,” he said, adding that it was more important to “do the right deal” over dismantling Pyongyang’s arsenal.

Kim, for his part, maintained that he was willing to denuclearize, though it was unclear whether his definition of that process matched Trump’s. Asked by a reporter in the morning if he was ready to give up his nukes, Kim replied: “If I was not, I wouldn’t be here.”

Trump called Kim’s comment possibly “the best answer you’ve ever heard.”

However, he acknowledged at the post-summit news conference that Kim “has a certain vision” of denuclearization that differed from the U.S. position.

“It’s not exactly our vision,” he said, “but it is a lot closer” now.

Trump had repeatedly touted the U.S. and its allies’ abilities to pour development cash into the poverty-stricken country as the most powerful tool in his arsenal before and during the talks. But experts noted that economic carrots had long failed to entice the Kim dynasty, which built up its nuclear program as part of a deterrent preventing regime change.

“Trump touts economic incentives for North Korea because he doesn’t understand North Korea and Kim,” Jackson said. “Plus money and status is all he thinks people care about because it’s all he cares about. So Trump thinks he can inflate Kim’s legitimacy and throw money at him and he’ll denuclearize. That’s ignorance in action.”

On the issue of human rights, Trump was asked by reporters about the case of American college student Otto Warmbier, who died after being detained in the isolated country. Warmbier’s parents have insisted that the Kim regime was at fault, but Trump said he did not believe the North Korean leader was himself aware of Warmbier’s death.

“He tells me that he didn’t know about it, and I will take him at his word,” the president said.

Warmbier, a 22-year-old University of Virginia student from Ohio, was visiting North Korea with a tour group when he was arrested and sentenced to 15 years of hard labor in 2016 on suspicion of stealing a propaganda poster. He died in June 2017, shortly after being returned to the U.S. in a coma.

The North is known for its abysmal human rights record, but the issue has largely taken a backseat to the issue of denuclearization in the two countries’ talks.

Now, with both parties having to return to their respective countries with nothing to show for their efforts, experts said the relationship could enter into a deep freeze.

“I think we’ll be in a twilight zone for a while, but I also think this is the end of any serious bilateral nuclear negotiations between the U.S. and DPRK under this administration,” Griffith University’s O’Neil said, using the acronym for the North’s official name, the Democratic People’s Republic of Korea.

O’Neil said the risk with that scenario is that Kim will embrace a narrative that the U.S. “stabbed North Korea in the back” and that he has little choice but to accelerate the nuclear and missile programs, possibly through resuming weapons testing.

“If the latter occurs, Trump will feel compelled to act and we could see ourselves back in the second half of 2017,” he said.

Still, he said a more likely sequence of events would see Pyongyang and Washington entering into a holding pattern of sorts for the foreseeable future.

“The denuclearization agenda has been effectively shredded — Pyongyang has refused to engage at any point with an accounting of its program as a first step to verification — so it’s hard to see what possible rationale there would be for Trump and Kim to meet again,” O’Neil said.