US President Donald Trump said on Tuesday there was a "substantial chance" his summit with North Korean leader Kim Jong-un will not take place as planned on June 12 amid concerns that Kim is resistant to giving up his nuclear weapons.
A small group of global journalists have been invited to watch the demolition.
"We'll see what happens".
The journalists from the MBC television network and News1 wire service took a special government flight later Wednesday to go to the North's northeastern coastal city of Wonsan.
North Korea has been clearing out small buildings and sheds from the site in recent weeks, according to satellite images and analysis from the online Korea journal 38 North.
North Korea is demanding the return of 13 defectors to the South as a condition for the resumption of talks with Seoul, with support groups for thousands who have fled the repressive regime in the North saying there is genuine fear that Seoul might give in to Pyongyang's demands and that their lives might be at risk.
Trump said that while the U.S.is still preparing to sit down with Kim - and even offer him protection in exchange for ramping down the North Korean nuclear program - he acknowledged that things could change.
But there has been increasing pessimism about the meeting after North Korea scrapped the inter-Korean talks and threatened to do the same for the Kim-Trump summit in protest of the South Korea-U.S. military drills and what it calls Washington's push for "one-sided" disarmament.
Pompeo, who was director of the Central Intelligence Agency before becoming secretary of state in April when Trump fired Rex Tillerson, has met twice with Kim in Pyongyang.
Technical experts have not been invited to the decommissioning of the site, raising further questions whether the gesture is for show. Sceptics say the site has already outlived its usefulness with six successful nuclear tests in the bag and can quickly be rebuilt if needed.
38 North, a US website dedicated to monitoring developments in North Korea, earlier reported that satellite imagery shows that North Korea is preparing to build an observation stand for the dismantling of its nuclear test site.
Go Myong-hyun, an analyst at the Asan Institute for Policy Studies, said both sides were playing "a game of chicken" in the run up to the summit "to gain an upper hand in negotiations".
From there they are expected to travel for some 20 hours up the east coast by train and bus to the remote test site - a vivid illustration of the impoverished country's notoriously decrepit transport infrastructure.
High-level intra-Korea talks will likely resume after Friday, once Max Thunder finishes, Moon's media secretary Yoon Young-chan said. But Seoul says the group did not make the flight after Pyongyang declined to accept them.
Pompeo said he had raised the issue of human rights with Kim "and it will be part of the discussions as we move forward". "They must know what price they will be made to pay", the commentary said, using the North's traditional lowercase "s" when describing the South.
"We delivered a list of eight reporters from two outlets to the North today, and the North accepted it", the ministry said in a statement on Wednesday.
Joel Wit, director of 38 North and a senior fellow at the Stimson Center, said dismantling the site is not a meaningless gesture, as there are two areas of the installation that have never been used for tests and still contain tunnels.
The other journalists from the United States, the U.K, China and Russian Federation, including an Associated Press Television crew, had arrived in Wonsan on Tuesday.