US President Donald Trump has now said there is no hurry to denuclearise North Korea, having previously said the process would start very soon.

"Discussions are ongoing and they're going very, very well," Mr Trump told reporters in Washington.

"We have no time limit. We have no speed limit," he added.

Mr Trump also said he discussed North Korea with Russian President Vladimir Putin at their summit in Helsinki on Monday.

"President Putin is going to be involved in the sense that he is with us," Mr Trump said.

President Trump met Kim Yong-un on 12 June for an unprecedented summit in Singapore, during which the North Korean leader repeated a pledge to denuclearise his country.

But the accord did not spell out a timetable for the process or say how it would be carried out. Diplomats are now expected to hammer out the details.

More than a month later, no concrete progress has been reported and North Korea has complained the US is making unilateral demands.

Before the Singapore summit, the Trump administration said denuclearisation should start "without delay," and after the meeting, it spoke of the process beginning "very quickly".