The summit between President Trump and North Korean leader Kim Jong Un ended earlier than expected without an agreement due to North Korean demands to lift U.S.-led sanctions.
Earlier, both Trump and Kim had expressed hope for progress on improving relations and on the key issue of denuclearization, in their talks in the Vietnamese capital, Hanoi.
"Basically, they wanted the sanctions lifted in their entirety, but we couldn't do that ... we had to walk away from it," Trump told reporters after summit talks were cut short.
Both leaders left the venue of their talks without attending a planned lunch together.
The United Nations and the United States ratcheted up sanctions on North Korea when the reclusive state undertook a series of nuclear and missile tests in 2017, cutting off a cash supply.
Failure to reach an agreement marks a setback for Trump, a self-styled dealmaker under pressure at home over his ties to Russia and testimony from Michael Cohen, his former personal lawyer, accusing him of breaking the law while in office.
Trump said Cohen "lied a lot" during Congressional testimony in Washington on Wednesday.
While Trump had said he was in "no rush" to strike a deal with North Korea, and wanted to do the right deal with Kim.
The White House had been confident enough to schedule a now canceled "joint agreement signing ceremony" at the conclusion of talks.