After a summit in Pyongyang, Kim and South Korean President Moon Jae-in said the North was also willing to close its main nuclear complex but only if the United States took unspecified reciprocal action.

The pledges Kim and Moon made at their third summit this year could inject fresh momentum into the stalled nuclear negotiations between Washington and Pyongyang and lay the groundwork for another meeting Kim recently proposed to U.S. President Donald Trump.

Kim pledged to work toward the “complete denuclearization of the Korean Peninsula” during his two meetings with Moon earlier this year and at his historic June summit with Trump in Singapore.

But discussions over how to implement the commitments have since faltered. Washington is demanding concrete action toward denuclearization, such as a full disclosure of North Korea’s nuclear and missile facilities, before agreeing to key goals of Pyongyang – declaring an official end to the 1950-53 Korean War and easing tough international sanctions.

Trump welcomed the latest pledges, saying they were part of “tremendous progress” with Pyongyang on a number of fronts, and hailed the “very good news” from the Korean nations’ summit.

“He’s calm, I’m calm – so we’ll see what happens,” Trump told reporters at the White House, referring to Kim. “It’s very much calmed down.”

Speaking at a joint news conference in Pyongyang, the two Korean leaders agreed to turn the Korean Peninsula into a “land of peace without nuclear weapons and nuclear threats.”

Kim said he would visit Seoul in the near future, in what would be the first-ever visit to the South Korean capital by a North Korean leader.

Kim’s latest promises come days before Moon meets Trump in New York at the U.N. General Assembly next week.

As a next step, North Korea will allow experts from “concerned countries” to watch the closure of its missile engine testing site and launch pad in the northwestern town of Dongchang-ri, according to a joint statement signed by Moon and Kim. The facilities were a key test center for North Korea’s intercontinental ballistic missiles designed to reach the United States.

The North also “expressed its readiness” to take additional measures, such as a permanent dismantlement of its main nuclear facilities in Yongbyon should there be unspecified corresponding action from the United States, according to the statement.

Those U.S. steps could include an end-of-war declaration, South Korea’s national security adviser Chung Eui-yong told reporters.

The neighbors remain technically at war because the Korean War ended in armistice and not a peace treaty.