The South Korean government is trying to keep up the momentum in diplomatic efforts to resolve the North Korean nuclear question, announcing Sunday that the North would dismantle its main nuclear test site next month and that its leader, Kim Jong Un, was prepared to meet with Japanese Prime Minister Shinzo Abe.

The South’s presidential Blue House also revealed a symbolic step of goodwill from Kim: North Korea would move its clock forward half an hour to return to the same time zone as Seoul and Tokyo.

This came two days after a historic summit between South Korea’s Moon Jae-in and Kim, which resulted in a joint statement containing a vague agreement to work toward the “complete denuclearization” of the Korean Peninsula.

Kim pledged to dismantle the nuclear test site at Punggye-ri, in the north of his country, in May, a Blue House spokesman said Sunday.

“Some say that we are terminating facilities that are not functioning, but you will see that we have two more tunnels that are bigger than the existing ones and that they are in good condition,” Moon’s chief press secretary, Yoon Young-chan, quoted Kim as saying.

There have been reports that the test site, buried under Mount Mantap, was suffering from “tired mountain syndrome” and was unusable after September’s huge test, which caused an earthquake so big that satellites caught images of the mountain above the site actually moving.

But numerous nuclear experts have cast doubt on that theory, and Kim apparently did, too.

Kim said he would invite security experts and journalists to the North to observe the closure of the site, Yoon said.

In Washington, national security adviser John Bolton said the Trump administration isn’t “starry-eyed” about Kim’s promises. The United States, he said on “Fox News Sunday,” isn’t ready to ease sanctions or offer other concessions to North Korea before Pyongyang fully commits to denuclearization.

The White House, though, continues to prepare for an upcoming meeting between Trump and Kim, and Bolton said Sunday that the details are being negotiated.

“We need to agree on a place, and that remains an issue,” he said. “But if, in fact, Kim has made a strategic decision to give up his entire nuclear weapons program, then I think deciding on the place and the date should be fairly easy.”

There are other issues, Bolton said, that the administration wants to press soon, if not immediately: “ballistic missiles, chemical and biological weapons, the American hostages, the Japanese abductees.”

Secretary of State Mike Pompeo, in an interview Sunday with ABC News, also brought up the issue of three Americans who are being held by North Korea. Pompeo, who secretly met with Kim in North Korea over Easter weekend, said while on a visit to Israel on Sunday that Kim would not be alarmed about American intentions even if the Trump administration withdrew from the Iran nuclear deal.

This is not the first time North Korea has invited outside experts to witness the shutdown of some aspect of its nuclear program. In 2008, Pyongyang invited international journalists to film the destruction of the cooling tower at the Yongbyon nuclear reactor, from which it had been harvesting plutonium to make its first bombs.

It turned out that North Korea was building a separate uranium enrichment facility so it could continue to produce fissile material even without Yongbyon.

Kim reportedly said while meeting with Moon that he had no intention of using his nuclear weapons against neighboring countries. 

“Although I am inherently resistant toward America, people will see that I am not the kind of person who fires nukes at South Korea, the Pacific or America,” Kim said during the summit, Yoon told reporters Sunday.

“Why would we keep nuclear weapons and live in a difficult condition if we often meet with Americans to build trust and they promise us to end the war and not to invade us?” Yoon quoted Kim as saying.

That will be viewed as disingenuous, to say the least, given that Kim’s representatives and North Korean state media outlets repeatedly threatened last year to fire nuclear-tipped missiles at the United States and to detonate a hydrogen bomb over the Pacific.

But this is a new year, and Kim, in a strong position having obtained demonstrably functional nuclear weapons and missiles, appears ready to deal.  

Kim also said he would turn the clocks forward in North Korea to put them back in sync with South Korea and Japan, Yoon said. 

In 2015, on Aug. 15 — the day the Koreas mark their independence from Japan’s colonial rule — the Kim regime put the clocks back half an hour to create the “Pyongyang time” zone. It framed the decision as a rebuke to Japan.

South Korea’s progressive president wants to use his summit with Kim as a springboard to improve Pyongyang’s relations with Tokyo and, particularly, with Washington.

Moon and President Trump spoke on the phone for 75 minutes on Saturday night Seoul time and agreed that South Korea and the United States should continue to closely coordinate “so that the planned U.S.-North Korea summit generates an agreement on concrete measures to realize complete denuclearization,” the Blue House spokesman said.

Trump tweeted afterward that he “had a long and very good talk with President Moon of South Korea.” 

“Things are going very well, time and location of meeting with North Korea is being set,” Trump wrote. “Also spoke to Prime Minister Abe of Japan to inform him of the ongoing negotiations.”

Moon also spoke with Abe over the weekend and “offered to lay a bridge between North Korea and Japan,” another Blue House spokesman said. 

Moon and Chinese Premier Li Keqiang are expected to meet in Tokyo for a trilateral meeting with Abe — a significant breakthrough in the frosty relations in the region — on May 9.

Moon will then travel to Washington for a meeting with Trump about the latter’s summit with Kim, expected to take place at the end of May or beginning of June.

Influential members of Congress expressed some doubts Sunday about relations with North Korea.

“A lot of what they are agreeing to now, they have agreed to in the past. And as it has turned out, they have something very different in mind when they talk about denuclearization,” said Rep. Adam B. Schiff (Calif.), the top Democrat on the House Intelligence Committee, during an appearance on ABC News’s “This Week.”

Speaking on CNN, Sen. James Lankford (R-Okla.) said he would not have described Kim as “honorable,” as Trump did last week after months of mocking the North Korean leader.

“I think [Trump] is better to be able to just call him ‘rocket man’ and to be able to stick with that than honorable, just because he is a ruthless dictator that does public executions of anyone who disagrees,” Lankford, a member of the Senate Intelligence Committee, told “State of the Union.”

Tony Romm in Washington and Carol Morello in Tel Aviv contributed to this report.