"I explained to President Trump that his leadership and his maximum pressure policy, together with worldwide solidarity, brought us to this juncture".
Mr Kim made light-hearted remarks about how he is viewed outside North Korea in worldwide media and elsewhere, one Blue House official said.
Sanders suggested North Korea would need to take steps toward denuclearizing, though North Korea has not made any commitment to do that before talks take place. And a senior Administration official said it would happen in "a couple of months" but the "exact timing and place is still to be determined".
For his part, Sanders, a presidential contender in the 2016 election, said that he is "very anxious about North Korea's nuclear capability" and seemed skeptical that Trump is taking diplomacy seriously.
This comes at a time when the US State Department is severely under-staffed, and just a week after the department's highest level official on North Korea, Joseph Yun, left. -South Korea alliance and the elimination of the USA nuclear umbrella that extends to its allies in Northeast Asia - including Japan.
"We are not going to have this meeting take place until we see concrete actions that match the words and the rhetoric of North Korea", White House spoekeswoman Sarah Sanders said at a news briefing.
The president had done what presidents from Eisenhower forward have tried - opened a relationship with the most isolated and perhaps risky country on earth, got the North Koreans to talk of denuclearization and even to acknowledge the need for the annual joint U.S. The exercises there are seen as preparation for an attack on Pyongyang, while the South Koreans and Americans characterize them as defensive in nature.
For decades, the Kim family has sought consistently and unsuccessfully to be recognized as the legitimate rulers of North Korea.
January 1, 2018: Kim says in his New Year's address that he has a nuclear button on his desk, but also calls for improved relations with South Korea and suggests sending a delegation to the Winter Olympics in Pyeongchang, South Korea.
"They don't for example have an ambassador to South Korea at the moment".
Ivanka Trump at the Pyeongchang Winter Olympics in February.
As the Trump Administration hammers down its own position and goals for the meeting, traditionally officials below the President would also be reaching out to officials in North Korea and other countries with a stake in the outcome in advance of the summit. Trump tweeted, in response, that "great progress [was] being made".
Kim, eager to end worldwide sanctions and prevent military action by the USA, has signaled a possible readiness to denuclearize. "So I think people in South Korea are more kind of immune to all of the noise", Kim said. The tests were part of efforts to ideal an Intercontinental Ballistic Missile (ICBM) with a survivable warhead to target USA mainland cities.
President Xi Jinping told Trump in a phone call on Friday that he appreciates his desire to resolve the North Korea issue politically, Chinese state media said.
Mr Trump's meeting the despot formally known as "little rocket man" will not necessarily be a total flop.
Trump's North Korea rants hit their height between August and October past year, when he repeatedly called Kim "rocket man," described him as "a madman", and threatened North Korea with "fire and fury".