US Secretary of State Mike Pompeo on Sunday urged North Korea to follow the example of Vietnam, saying President Donald Trump believed Pyongyang could replicate Hanoi's path to normal relations with Washington and to prosperity.

But for that to happen, its leader Kim Jong Un needed to seize the moment.

Speaking to business executives in the Vietnamese capital Hanoi, Pompeo said he hoped the United States could one day share the same level of partnership with North Korea as it did with Vietnam, a long-time former enemy.

His comments followed two days of frosty talks in Pyongyang aimed at persuading Kim to give up nuclear weapons, which prompted North Korean accusations he had used "gangster-like" diplomacy.