there is no longer a Nuclear Threat from North Korea.” When Mr. Kim and Mr. Trump met again in 2019 in Hanoi, Vietnam, the negotiations went nowhere, and the men left without an agreement on how to move forward with the Singapore deal.

While Mr. Moon was careful to dole out praise for Mr. Trump, he also seemed frustrated by the former president’s erratic behavior and Twitter diplomacy. Mr. Trump canceled or downsized the annual joint military drills that the United States conducts with the South and demanded what Mr. Moon called an “excessive amount” to keep 28,500 American troops in South Korea.

strike a deal within 46 days of Mr. Biden’s inauguration was a “clear testament to the importance President Biden attaches to” the alliance.

Mr. Moon is hopeful about the progress the new American leader can make on North Korea, although any significant breakthrough may be unrealistic, given the deep mistrust between Washington and Pyongyang.

Mr. Biden said last month that he was “prepared for some form of diplomacy” with North Korea, but that “it has to be conditioned upon the end result of denuclearization.”

North Korea has offered ideas on a phased approach starting with the demolition of its only-known nuclear test site, followed by the dismantling of a rocket engine test facility and the nuclear complex in Yongbyon north of Pyongyang.

Mr. Moon said he believed such steps, if matched with American concessions, could lead to the removal of the North’s more prized assets, like I.C.B.M.s. In that scenario, he said, the move toward complete denuclearization becomes “irreversible.”

“This dialogue and diplomacy can lead to denuclearization,” he said. “If both sides learn from the failure in Hanoi and put their heads together for more realistic ideas, I am confident that they can find a solution.”

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