Donald Trump’s second summit with Kim Jong-un ended early on Thursday after the US president refused North Korea's demand for the lifting of all sanctions imposed over its nuclear programme.
The two leaders had been scheduled to hold a working lunch on the second day of their meeting in Hanoi, followed by the signing of a joint agreement at 2pm. However, both events were abruptly cancelled and their motorcades were seen leaving the summit venue in the Vietnamese capital at 1.30pm.
"It was about the sanctions," Mr Trump told reporters at a press conference soon afterwards. "Basically, they wanted the sanctions lifted in their entirety, and we couldn't do that."
The United Nations and the US tightened sanctions on North Korea after a flurry of nuclear and missile tests in 2016-2017.
No tests have been conducted since late 2017, and Mr Trump said Mr Kim had promised that they would not be resumed.
"He said he's not going to do testing of rockets or missiles or anything that has to do with nuclear," the US president said.
The White House said the two leaders had "very good and constructive meetings in Hanoi”.
"No agreement was reached at this time, but their respective teams look forward to meeting in the future,” spokeswoman Sarah Sanders said in a statement announcing the early conclusion of the summit.
Joe Cirincione, president of the Ploughshares Fund peace foundation, said on Twitter that failure to reach an agreement was "a major failure" that showed the limits of holding a summit without proper preparation.
The second meeting of the US and North Korean leaders had raised hopes of a more concrete outcome than the vaguely worded statement issued after their first summit in Singapore in June last year. That agreement said both sides would work towards the denuclearisation of the Korean Peninsula but offered no timetable or mechanism for achieving this.
The two leaders resumed talks on Thursday with both expressing hope for progress on improving relations and on denuclearisation.
“If I’m not willing to do that, I won’t be here right now,” Mr Kim told reporters through an interpreter, when asked if he was ready to give up his nuclear weapons.
Mr Trump, responding to that, said: "That might be the best answer you’ve ever heard.”
However, Mr Trump had downplayed hopes for a breakthrough in Hanoi.
“Speed’s not that important to me,” he said as he began talks with Mr Kim at the Sofitel Legend Metropole hotel on Wednesday. “No rush. We just want to do the right deal.”
He repeated his position after the talks collapsed on Thursday, telling reporters: "I'd much rather do it right than do it fast."
The summit was organised in Hanoi in haste after Mr Trump announced the meeting on February 8, and the White House sought to lower expectations. Other possible outcomes expected from the meeting included a joint declaration that the US and North Korea were no longer at war, a nonbinding agreement that would not officially replace the 1953 armistice that ended the Korean War.
South Korea regretted that the talks had not resulted in a deal but said "meaningful progress" had been made.
"It is regrettable President Trump and North Korean leader Kim Jong -un did not reach a complete agreement on today's summit," a spokesman for President Moon Jae-in said.
"But it appears clear that more meaningful progress was made than at any other point in the past."
Mr Trump left Vietnam on Thursday while Mr Kim remained for a state visit that ends on Saturday.