North Korea agreeing to discuss denuclearisation "is evidence that President [Donald] Trump's strategy to isolate the Kim regime is working," US Vice-President Mike Pence has said.

He said the US had made "zero concessions" and "consistently increased the pressure" on North Korean leader Kim Jong-un.

An unprecedented summit between the two leaders is due to take place by May.

It comes only months after the pair hurled insults at each other.

In recent months, Mr Trump has belittled Mr Kim as the "rocket man", threatening him with "fire and fury", while Mr Kim has called Mr Trump "a mentally deranged US dotard".

Mr Trump has hailed the dizzying shift in North Korea's position as "great progress" but said sanctions would remain in place. No sitting US president has ever met a North Korean leader.

South Korea's President Moon Jae-in said the news of the Kim-Trump meeting had come "like a miracle" and was a step towards denuclearisation.