The surprise development follows months of tension between the two nations, during which the North Koreans have conducted a series of military exercises and fired nuclear missiles over Japan in a show of strength.
The rare face-to-face encounter with Kim will have given USA and South Korean officials invaluable intelligence on the leader, his personality and potentially his negotiating style.
Still, the White House indicated that planning for the meeting was fully on track.
He noted that Bill Clinton came close to visiting North Korea only after five years of negotiations, a process the memory of which now reminds the world of how the situation on the peninsula has festered for decades. "Time and place to be determined", Trump tweeted late Friday. It would be all the more remarkable given the history of insults, threats and challenges exchanged by the two leaders.
Mr Davis told SBS News the idea of President Trump and Kim Jong-un meeting alone made him nervous.
Signs of a thaw emerged this year, with North and South Korea resuming talks and North Korea attending the Winter Olympics. Kim has called Trump a "deranged USA dotard", a "lunatic" and a "loser". The Kim regime's long-running control of North Korea could not have existed without significant support from the communists in Beijing.
There are many details to be ironed out before any Trump-Kim meeting could take place, not least the location.
Chung extended the invitation from Kim to meet while briefing Trump on the four-hour dinner he had with the North Korean leader in Pyongyang on Monday, following which he flew quickly to Washington. Let me just say, though, Donald Trump was elected because of his willingness to do things that other politicians and presidents haven't done, and this is right along the lines of that so I won't be critical of it.
In the first months of his presidency, Donald Trump played the Chinese paper to push North Korea and approached the Japanese Prime Minister, Sino Ampe, giving the impression that South Korea's President Mou Jie-in was on the sidelines.
Finally, in 2008, six-party talks were held in Beijing to address the nuclear issue, but broke down over North Korea's refusal to allow global inspectors unfettered access to suspected nuclear sites.
"The fundamental definition of denuclearization is quite different between Washington and Pyongyang", Revere said, noting that as recently as January 1, Kim had vigorously reaffirmed the importance of nukes for North Korea's security.
Kim might even free several American citizens now detained in the North to brighten the atmosphere of his summit with Trump, Choi said.
The United States and North Korea fought on opposite sides of a war in the 1950s, and in the last two decades have been engaged in perhaps the world's most risky nuclear standoff, with 30,000 U.S. military personnel stationed just over the border in the South. "Otherwise we are setting ourselves up for a major diplomatic failure". Right now, Kim Jong Un is setting the agenda and the pace, and the Trump administration is reacting.
They were further wrong-footed when Kim sent his trusted sister to the Games bearing an invitation to South Korean President Moon Jae-in to meet and talk. "An American President visits Pyongyang, compelled by North Korea's nuclear and missile programmes".