"Several key operational support buildings, located just outside the North, West and South Portals, have been razed" since April 24, write Frank V. Pabian, Joseph S. Bermudez Jr. and Jack Liu.
In a statement carried by state media, North Korea's Foreign Ministry said all of the tunnels at the country's northeastern testing ground will be destroyed by explosion, and observation and research facilities and ground-based guard units will also be removed.
The North Korean announcement said the ceremony would take place between May 23 and 25, weather permitting.
"The Nuclear Weapon Institute and other concerned institutions are taking technical measures for dismantling the northern nuclear test ground ... in order to ensure transparency of discontinuance of the nuclear test", North Korean press agency KCNA said earlier this week.
But the interview remarks suggest the focus of the summit will likely be laser sharp, avoiding subjects which precedence has shown can draw sharp North Korean sensitivities.
Kim declared his nuclear force as complete in December, following North Korea's most powerful nuclear test to date in September and three flight tests of ICBMs created to reach the USA mainland. Trump called the action "a very smart and gracious gesture!" on Twitter and told reporters that the process "is very important".
North Korea's plan to close the site has been welcomed by Washington, Seoul and the United Nations secretary general.
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The Trump administration argues that it will only negotiate with North Korea "The complete, verifiable and irreversible dismantling" of its nuclear program, something that regime has always refused to consider essential to its survival.
According to the KCNA announcement, the North will invite local press, but global media will be limited to journalists from China, Russia, South Korea, Britain and the United States, due to the testing ground's "small space".
The dictator met with South Korean president Moon Jae-in last month in historic talks which saw both leaders commit to denuclearisation of the Korean Peninsula and a formal end to the Korean War - 65 years after hostilities ended.
On Saturday, he told Reuters that closure of Punggye-ri did not mean much in terms of disarmament, given that the United States, for example, stopped nuclear testing in 1992.
While satellite imagery indicates that the north portal of the test-site has been abandoned after the damage caused by the quake, two of the other areas, approximately 2.5 and 3.5 kilometers from the peak of the mountain, remain accessible through the south and west portals.
The decision to dismantle the test facility now may be politically expedient for Kim, but having perfected a crude nuclear deterrent and ballistic missiles thought capable of delivering it as far as the continental United States, the North Korean leader may no longer need the underground test facility.
Satellite photos from last month showed signs of construction at the North's Yongbyon nuclear facility.