US Secretary of State said it would be "nothing short of tragic to let this opportunity go to waste"
The US Secretary of State Mike Pompeo says "real progress" has been made towards setting up the conditions for an historic summit with North Korea.
Mr Pompeo says the secretive state is "contemplating a strategic shift", and said that talks to prepare a meeting are going well.
He has been holding talks in New York with Kim Jong Un's right-hand man, Kim Yong Chul.
The senior official will travel to Washington to personally deliver a letter to Donald Trump from the North Korean leader.
Speaking after the meeting, Mr Pompeo said: "Through these series of meetings, I'm confident we're moving in the right direction.
"Today vice-chairman Kim and I discussed our countries could come together and take advantage of the unique opportunity that our two leaders have created through their visions of the future.
"Our two countries face a pivotal moment in our relationship, in which it could be nothing short of tragic to let this opportunity go to waste."
Mr Pompeo - who has visited North Korea twice in recent months - added that he has made it 'very clear' to North Korean officials that the US objective is for the "complete, verifiable and irreversible denuclearisation of the Korean peninsula".
He noted that there "remains a great deal of work to do", but stressed that progress had been made.
On the summit itself, he said he can't say yet whether the meeting - initially proposed for June 12th in Singapore - will go ahead.
However, he added: "It does no good if we're in a place where we don't think there's real opportunity to placing [Donald Trump and Kim Jong Un] together... [but] we've made real progress [...] in the last 72 hours."
Recent weeks seen increased uncertainty over the proposed summit, with Donald Trump having personally written to the North Korean leader to call off the summit last week.
However, both sides have since reiterated their wish to go ahead with the summit.