Donald Trump will hold a second summit with North Korean leader Kim Jong Un around the end of February, the White House said on Friday after the US president met Pyongyang's top nuclear negotiator.

The announcement came amid a diplomatic flurry in Washington surrounding the visit of North Korean envoy Kim Yong Chol and marked a rare sign of movement in a denuclearisation effort that has stalled since a landmark meeting between Trump and the North Korean leader in Singapore last year.

"President Donald J Trump met with Kim Yong Chol for an hour and half, to discuss denuclearisation and a second summit, which will take place near the end of February. The President looks forward to meeting with Chairman Kim at a place to be announced at a later date," White House spokesman Sarah Sanders said in a statement.

Despite the summit announcement, there has been no indication of any narrowing of differences over the US demands that North Korea abandon a nuclear weapons programme that threatens the US or over Pyongyang's demand for a lifting of punishing sanctions.

Trump declared after the Singapore summit in June that the nuclear threat posed by North Korea was over.

But hours before Kim Yong Chol's arrival on Thursday, Trump unveiled a revamped US missile defence strategy that singled out the country as an ongoing and "extraordinary threat".

On Friday, Sanders said the US continues to make progress in its denuclearisation talks with North Korea, but will keep sanctions on Pyongyang in place.

Trump's meeting with the North Korean envoy came after Kim Yong Chol met Secretary of State Mike Pompeo and US special representative for North Korea, Stephen Biegun, for a meeting aimed at clearing the way for a second summit between the US president and the North Korean leader.

The State Department described the meeting as a "good discussion" between the envoys on efforts to make progress on commitments made during the Trump-Kim summit last June.

Trump has spoken several times about having a second summit with Kim early this year and has exchanged multiple letters with the North Korean leader despite little tangible progress on a vague denuclearisation agreement reached at their meeting in Singapore last June.

Since then, several private analysts have published reports detailing continuing North Korean development of nuclear and missile technology.

'Promising' steps

Friday's meeting came months after planned talks between the two in November were called off at the last minute.

Contact between the two sides resumed after a New Year's speech by North Korea's leader, in which he said he was willing to meet Trump "at any time", Cho Yoon-je, the South Korean ambassador to the US, told reporters last week.

Talks had stalled over North Korea's refusal to provide a detailed accounting of its nuclear and missile facilities that would be used by inspectors to verify any deal to dismantle them. North Korea has been demanding that the US lift harsh sanctions and provide it with security guarantees before it takes any steps beyond its initial suspension of nuclear and missile tests.

At a conference of US diplomats at the State Department on Wednesday, Vice President Mike Pence acknowledged the lack of progress.

He called the Trump-Kim dialogue "promising" but stressed that "we still await concrete steps by North Korea to dismantle the nuclear weapons that threaten our people and our allies in the region".

Last week, South Korean President Moon Jae-In urged Pyongyang to take "bold, practical measures for denuclearisation" to ensure sanctions are lifted but stressed that "corresponding measures" were also needed from Washington, such as agreeing a "peace regime" and formally declaring an end to the 1950-53 Korean War.

His comments came as Kim Jong Un visited China - North Korea's key ally - for talks with President Xi Jinping.