In a highly unusual late-night statement at the North Korean delegation's hotel, foreign minister Ri Yong Ho said Pyongyang had made a "realistic proposal" at the summit in Hanoi.

He denied Trump's assertion that Pyongyang had demanded the lifting of all sanctions imposed on it over its nuclear weapon and ballistic missile programmes.

"If the US releases partial sanctions namely... those that hamper the civilian economy and the livelihood of our people, we will permanently and completely dismantle all the nuclear production facilities in the Yongbyon area, in the presence of US experts," Ri told reporters.

The minister was reading a statement after the two-day Trump-Kim talks closed with no final deal and the US president gave a press conference before flying out of Vietnam.

The much-anticipated second summit between the two leaders ended with no agreement reached and a scheduled signing ceremony was dropped.