Hanoi: North Korea's Foreign Minister held a midnight press conference to dispute US President Donald Trump's account of why the two sides had failed to strike a deal at the Hanoi summit.

The unusual press conference was called hours after Trump had left Hanoi and had blamed North Korea for demanding full sanctions relief.

North Korean Foreign Minister Ri Yong-ho said his country sought the partial lifting of United Nations' sanctions in return for the dismantling of the Yongbyon nuclear reactor.

Ri said it was willing to pledge in writing to permanently end nuclear and long-range missile tests.