The meetings between the two leaders in Hanoi, Vietnam started Wednesday night and were scheduled to conclude with a signing ceremony for some sort of agreement between the two nuclear powers. Instead, the talks were cut short on Thursday — even before Trump and Kim could share a planned lunch — and the White House announced there would be nothing to sign.
"It wasn't a good thing to be signing anything," Trump said during a post-summit news conference. "We had some options, and at this time we decided not to do any of the options, and we'll see where that goes."
"Sometimes you have to walk, and this was just one of those times," he added.
Trump is pushing North Korea to give up its nuclear weapons as he dangles the prospect of an economic boost to the repressive country. Kim, experts say, wants to see sanctions eased without losing the strategic benefits of his weapons of mass destruction.
Trump said he had not committed to a third summit with the North Korean dictator. Still, Trump described the talks as "productive," and highlighted his relationship with Kim — "I think we'll end up being very good friends."
At the end of the day, though, Trump said he "would not have been happy about" any deal he saw on the table for Thursday's talks.
"Basically, they wanted the sanctions lifted in their entirety and we couldn't do that," Trump said. "They were willing to denuke a large portion of the areas that we wanted, but we couldn't give up all of the sanctions for that. So we continue to work and we'll see, but we had to walk away from that particular suggestion. We had to walk away from that."
North Korea currently faces United Nations sanctions and separate sanctions from the United States. The U.N. blocks some imports and exports and has frozen the assets of individuals connected with Pyongyang's nuclear program. The United States restricts the North Korean economy further and targets more individuals.
Trump claimed Kim was willing to close down one weapons facility — the Yongbyon nuclear complex — in exchange for the complete removal of sanctions, but the U.S. team "brought many points up that they were surprised that we knew" and so demanded more actions from Kim's regime.
"(Kim) wants to denuke, but he wants to just do areas that are less important than the areas that we want. We know the country very well, believe it or not, we know every inch of that country," Trump said, adding that he thought the gap between the U.S. and North Korea would be bridged "with time."
The president confirmed that all the current sanctions on Pyongyang will remain in place.
"You always have to be prepared to walk," Trump said. "I could have 100 percent signed something today — we actually had papers ready to be signed — but it just wasn't appropriate. I want to do it right: I'd much rather do it right than do it fast."
Reflecting on the moment the American delegation decided to walk away from the negotiating table, Trump claimed the environment was "very good, very friendly."
"This wasn't a walk away like you get up and walk out. No, this was very friendly — we shook hands," he said. "When we walked away, it was a very friendly walk."
Secretary of State Mike Pompeo said during the news conference that the U.S. team had tried to lay the groundwork before the summit for an agreement, but Thursday's talks did not seal the deal.
"Unfortunately, we didn't get all the way. We didn't get to something that ultimately made sense for the United States of America," Pompeo said. "I think Chairman Kim was hopeful that we would. We asked him to do more and he was unprepared to do that."
The secretary of State specified that "even the Yongbyon facility in all of its scope — which is important for sure — still leaves missiles, still leaves warheads and weapons systems, so there's a lot of other elements we just couldn't get to."
Still, Pompeo said the two leaders had made "real progress" during their talks: "We are certainly closer today than we were 36 hours ago."
Trump said Kim promised him over dinner on Wednesday night that North Korea "is not going to do testing of rockets and nuclear."
"I trust him and I take him at his word," the president said.
Trump said "one of the first calls" he planned to make after the press conference would be to South Korean President Moon Jae-in, to discuss the events of the summit.
The meeting in Hanoi ended significantly earlier than scheduled as the White House declared there had been no new agreements reached during the summit.
"The two leaders discussed various ways to advance denuclearization and economic driven concepts," White House spokeswoman Sarah Sanders said. "No agreement was reached at this time, but their respective teams look forward to meeting in the future."
South Korean stocks fell on the news that the summit's schedule had been cut short.
Trump had repeatedly said at the start of Thursday's talks that his relationship with Kim was strong, and that he expected that connection to eventually carry the two nuclear powers to an agreement.
Although both sides say they've been making progress in recent months, this round of top-level talks had focused on many of the same issues as last June's Singapore summit. Trump had emphasized that he was willing to take his time on the talks as long as progress was being made.
"No rush. No rush. No rush. There's no rush, we just want to do the right deal. Chairman Kim and myself we want to do the right deal. Speed is not important, what's important is that we do the right deal," Trump told reporters at the start of the Thursday talks.
Asked during the post-summit news conference if he was still pushing for North Korea's "complete, verifiable denuclearization," Trump declined to lay out his position.
"I don't want to say that to you because I don't want to put myself in that position from the standpoint of negotiations — but, you know, we want a lot to be given up," he said.
—CNBC's Vivian Kam contributed to this report.