The second summit between President Donald Trump and the North Korean leader Kim Jong-un ended with no agreement after the US refused North Korean demands for sanctions relief, President Trump said.
"It was all about the sanctions," Trump told reporters. "They wanted the sanctions lifted in their entirety and we couldn't do that."
The two leaders had been expected to announce progress on denuclearization.
"Sometimes you have to walk and this was one of those times," Trump said.
At a news conference after the summit, in the Vietnamese capital of Hanoi, Trump said no plans had been made for a third summit, reports the BBC.
The original White House programme for the day had planned for a "Joint Agreement Signing Ceremony" as well as a working lunch for the two leaders, but expectations were abruptly dashed with the cancellation of both.
South Korea called the breakdown of talks "regrettable," but said it believed the US and North Korean leaders had made "more meaningful progress than at any time prior."
According to Trump, Kim made a significant offer – to dismantle all of the Yongbyon complex, the research and production facility at the heart of North Korea's nuclear programme. But in return Kim wanted all sanctions on North Korea lifted, something the US was not prepared to offer.
There was also a question over the network of facilities that extend beyond Yongbyon. Last month, Stephen Biegun, the US State Department special representative for North Korea, said North Korea had committed in pre-summit talks to destroy all of the nation's plutonium and uranium enrichment facilities, dependent on unspecified US measures in return.