"I am certain that a great outcome will be achieved this time that will be welcomed by all people," Kim told Trump. "I will do my best to make that happen."

The two men met at the Sofitel Metropole Hotel in the Vietnamese capital for 20 minutes of one-on-one talks before a small dinner with only close aides.

At their historic first encounter in Singapore in June, Kim signed a vague promise to work "towards the denuclearisation of the Korean peninsula", but the two sides have since disagreed over what that means.

"We came all the way to Hanoi to meet again," Kim said.

"When I think about, it was a period where we needed more thought, effort and patience than at any time," apparently referring to the eight months between their two meetings.