(CNN) North Korea outlined steps Saturday to dismantle its nuclear testing site -- and confirmed that international journalists, including those from the United States and the United Kingdom, would be invited to watch this month as its tunnels are blown up.

The announcement, by the Ministry of Foreign Affairs as reported by state news agency KCNA, came a day after Pyongyang pledged no longer to carry out unannounced missile tests or other activities that put flights at risk, according to a United Nations aviation agency.

North Korean leader Kim Jong Un previously announced the conclusion of North Korea's nuclear testing program and the intended shuttering of the Punggye-ri complex. He said April 20 that his nation already had "completed its mission" to test its weapons capability.

The statement Saturday gave greater details of the "technical measures" North Korea would take to dismantle the test site and "ensure transparency of discontinuance of the nuclear test."

US President Donald Trump expressed thanks to North Korea on Saturday evening, characterizing the announcement as a "very smart and gracious gesture" ahead of next month's nuclear summit in Singapore.

North Korea has announced that they will dismantle Nuclear Test Site this month, ahead of the big Summit Meeting on June 12th. Thank you, a very smart and gracious gesture! — Donald J. Trump (@realDonaldTrump) May 12, 2018

International journalists will be invited to conduct "on-the-spot coverage in order to show in a transparent manner" how the nuclear site is being put out of use, with a dismantlement "ceremony" scheduled for as early as May 23, depending on weather, the news agency said.

Since space is limited, only journalists from China, Russia, South Korea, the United States and the United Kingdom will be allowed access, according to KCNA.

First, explosives will be used to collapse the tunnels, KCNA said. Then, entries to the site will be blocked and all observation facilities, research institutes and guard structures will be removed. Guards and researchers will be withdrawn, and the area surrounding the test site will be closed.

Located in mountainous terrain in the northeast of the country, Punggye-ri is less than 100 miles (160 kilometers) from China.

South Korea's presidential office said last month that Kim planned to shut down his nuclear test site in May , following landmark talks between Kim and South Korea's President Moon Jae-in. Kim refuted claims by Chinese scientists that parts of the site had been so badly damaged by previous explosions, particularly its sixth and last test in September, that it may now be unusable , Moon's office added.

The latest developments come a day after US Secretary of State Mike Pompeo told reporters that he'd had "warm" and "good" conversations with Kim . His talks in North Korea were part of preparations for the planned summit on June 12

Missiles pledge

North Korea's pledge no longer to carry out unannounced missile tests or other activities that put flights at risk may be seen as the latest sign that the isolated nation is prepared to engage with the world.

Friday's statement from the United Nations' International Civil Aviation Organization (ICAO) followed a visit by its representatives to the North Korean capital earlier this week.

In addition to pledging an end to unannounced missile testing, North Korea said its "national nuclear arms program was complete," according to the UN agency.

The ICAO said it welcomed North Korea's collaborative approach and would work with adjacent states to facilitate and adopt these proposals.

Pyongyang's pledge could open the way for airlines to route flights through North Korean airspace. Earlier this month, North Korean officials asked to start an air route between the Pyongyang and Incheon, South Korea, airspace regions.

Kim last year oversaw a string of missile and nuclear tests , drawing the ire of the international community. Two of the North Korean missiles passed over the Japanese island of Hokkaido.

'Deep, complex challenges'

Pompeo spoke to reporters at the State Department following his return from North Korea to negotiate with Kim and retrieve three Americans held by the regime.

"We had good conversations, substantive conversations that involved deep complex challenges," Pompeo said Friday about his two meetings with Kim, who is known for assassinating rivals and family members and running prison camps throughout his country.

Pompeo met previously with Kim while CIA director, flying secretly to North Korea over the Easter weekend to discuss the possibility of a summit meeting with Trump and negotiations over North Korea's nuclear program.

Speaking Friday, Pompeo said any agreement with North Korea would have to include a "robust verification program" to ensure that Pyongyang complies. He added that the Trump administration was focused on making sure "we didn't end up where we were before" in the talks with North Korea.

Pompeo and other US officials have repeatedly said they are seeking North Korea's permanent verifiable denuclearization, while North Korean officials have said that they have already achieved their nuclear objectives.

Former US Secretary of Defense Ash Carter warned Friday that the United States should be cautious of any promises made by North Korea at the upcoming Trump-Kim summit.

Trump: 'Starting off on a new footing'

The summit, which has been in the works since Trump accepted Kim's invitation to meet in March, will be the first meeting between a sitting US president and North Korean leader.

Trump and South Korea's President are due to meet May 22 at the White House.

However, White House press secretary Sarah Sanders said she did not believe that Moon would be a part of the historic summit in Singapore the following month.

US President Donald Trump walks with the former US detainees on May 10, 2018, after their arrival at Joint Base Andrews in Maryland.

Trump struck an optimistic tone on North Korea as he personally welcomed home the freed American detainees early Thursday.

"We are starting off on a new footing -- I really think we have a very good chance of doing something very meaningful. A lot of very good things have happened," Trump said as he greeted the three former prisoners at Joint Base Andrews in Maryland.

"I really think he wants to do something and bring the country into the real world," he added of Kim. "It's never been taken this far, there has never been a relationship like this. I really think a lot of progress has been made."