Speaking to Channel 4 News, Mr Richardson claimed North Korea leader Kim Jong-un is a "rational" man despite his unpredictability.
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 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.”
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.”