Chung was in Washington with a delegation for a follow up meeting to one earlier in the week with Kim in North Korea.

Meeting at the White House for several hours prior to the announcement, the South Korean team briefed national security adviser HR McMaster, Defence Secretary James Mattis, Director of National Intelligence Dan Coats and Deputy Secretary of State John Sullivan.

The delegation hand-delivered a letter from Kim to the US President, Chung said. He used the White House forum to make the announcement, prior even to any tweets by Trump.

But the President didn't disappoint, two hours later he tweeted "Great progress being made but sanctions will remain until an agreement is reached. Meeting being planned!"

The White House had earlier followed with a statement confirming Trump would accept the invitation at a time to be determined.

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There was no word as to where the meeting would take place.

Prior to the announcement, some members of the administration urged caution, saying multiple diplomatic attempts to curb North Korean's nuclear program since the early 1990s had all failed, and that Kim's government may be seeking to get out of onerous sanctions or buy time to make a more advanced warhead.

"We're a long ways from negotiations," Secretary of State Rex Tillerson said in Ethiopia, where he was on a five-nation tour of Africa, on Thursday.

With agencies