The diplomatic crisis over North Korea's nuclear weapons program is widely seen as one of the gravest threats to international security. But South Korean President Moon Jae-in is optimistic that times are changing. In a speech delivered Tuesday at the Council on Foreign Relations in New York, during a program co-presented by Asia Society and the Korea Society, Moon said that "something miraculous is happening on the Korean peninsula" and expressed confidence that the relationship between U.S. President Donald Trump and North Korean leader Kim Jong Un is strong.

"President Trump and Chairman Kim trust each other," Moon said.

Earlier on Tuesday, President Trump spoke respectfully of Kim during an otherwise incendiary speech at the United Nations General Assembly, praising the North Korean leader for his "courage" in working toward denuclearization. Trump's tone stood in stark contrast to that of his address at the same event last year, when he said may have to "totally destroy" North Korea and stated that Kim was on a suicide mission. 

In the ensuing 12 months, however, Kim Jong Un has taken steps to end North Korea's diplomatic isolation. He has met multiple times with the government of China, North Korea's sole ally and economic patron, as well as with Moon — most recently last week in Pyongyang. And, three months after June's high-profile summit between Trump and Kim — the first meeting of a sitting U.S. president and North Korean leader ever — both leaders have said that they intend to meet again soon.

What accounts for Kim's decision to emerge from isolation? In a conversation with CFR President Richard Haass that followed his address, Moon said that Kim had expressed to him a genuine desire for economic development in North Korea, one of the world’s poorest and most isolated states, and that the North Korean leader would be willing to curtail Pyongyang's nuclear weapons program in exchange for security guarantees from the United States. Moon added that Kim, whom he referred to as a young man who "respects his elders," told him that he has no desire to deceive the international community because doing so would risk retaliation from the United States. In an acknowledgment of support for North Korea's desire for engagement, Moon called for international financial organizations to help rebuild North Korea's outdated infrastructure.

Granting economic concessions to North Korea, though, is contingent on Pyongyang taking concrete steps to dismantle its nuclear weapons program, something that it has repeatedly failed to do in the past. Moon acknowledged these previous disappointments — but said that the personal involvement of the two leaders indicates a greater chance for real rapprochement than in the past.

Moon has also taken great care to preserve South Korea's traditionally close relationship with the United States. On Monday, he and President Trump announced a revision of the U.S.-South Korea trade pact, which the American president had criticized as unfair to the United States. The new pact — which Asia Society Policy Vice President Wendy Cutler referred to as a "win-win deal with some solid improvements but nothing dramatic" — opens the South Korean market somewhat more to American imports.

During his appearance at CFR, Moon said that the strong relationship between Seoul and Washington would endure — even after a hypothetical reunion of the two Koreas.

The United States and South Korea "are not mere allies," he said. "But great allies."