The former Governor of New Mexico added that the rogue state dictator’s endgame could be to trade his military arsenal in exchange for economic subsidies from South Korea.
He said: “We’ve been there before, I know there have been two summits between North Korean and South Korean leaders that ended up disappointedly.
“But I think this Kim Jong-un man has an endgame.
“I think he’s a rational actor despite his unpredictability and some savage things that he’s done.
“I think in the end he wants to trade possibly his military arsenal for economic growth because this is one of the poorest countries on earth, a shattered economy, a Gulag situation in many cases, people are starving.
“I think that may be what he asks in return for the dismantling of his nuclear weapons, which I still think he’s not going to do.
“It’s going to take an awful lot if there is a final long-term agreement with North Korea.”
Kim Jong-un visited South Korea President Moon Jae-in on Friday, at the first Korean summit in over a decade.
The two Korean leaders agreed that the armistice that ended the Korean War in 1953 could become a peace treaty this year.
Speaking at a banquet later, Kim said: “We bade farewell to the frozen relationship between North and South Korea, which was a nightmare. And we announced the beginning of a warm spring to the world.”
Mr Moon declared a “new era of peace”, saying “there will be no more war”.
But many analysts remain cynical about the North’s enthusiasm for engagement. One theory says Kim agreed to freeze missile tests only because an underground nuclear site collapsed.
Previous goodwill pledges were abandoned after the North’s weapons tests and more conservative South Korean presidents.
But Kim said he and Mr Moon agreed to work to prevent a repeat of the region’s “unfortunate history”, in which progress “fizzled out”.
He said: “There may be backlash, hardship and frustration. A victory cannot be achieved without pain.”
In a joint statement he and Mr Moon agreed: An end to “hostile activities” between the nations and changing the demilitarised zone (DMZ) into a “peace zone” by ending propaganda broadcasts; An arms reduction pending the easing of military tension; To push for four-way talks involving the US and China; Organising a reunion of families left divided by the war; Connecting and modernising railways and roads across the border and further joint participation in sporting events, including this year’s Asian Games.
The commitment to denuclearisation does not explicitly refer to North Korea halting its nuclear activities, but aims for “a nuclear-free Korean peninsula”.