A satellite image released by a private US website monitoring North Korea shows that it has begun some work to dismantle a missile testing site, which its leader Kim Jong-un promised to US President Donald Trump in their June 12 summit.

The announcement by 38 North said that key facilities being dismantled at the site included a rail-mounted building, which is used to assemble missiles and rockets before they are moved to the launch pad. Also being dismantled is a rocket engine test stand that has been used to build liquid-fuel engines for missiles and space launch vehicles.

The 38 North report was followed by a news report in Seoul quoting a South Korean intelligence source as saying that the North appeared to have partially disassembled a tower crane at the same Sohae missile launch site.

The Yonhap News Agency report said that South Korean authorities detected activity on July 20 and 22 to partially disassemble the tower crane erected at the launch pad.

If the reports on the missile test site were true, it certainly would provide a positive momentum for the North Korean denuclearization talks that have made little progress since the historic US-North Korea summit held in Singapore. Dismantling a main missile test site was one of the promises Kim made to Trump in the summit.

What’s interesting is that the North did not make it public, in contrast to the destruction before the US-NK summit of a major nuclear test site, which it opened to international media. What one can guess is that given that US satellites cannot miss any such major activities at the missile testing site, the North wanted to demonstrate its sincerity and commitment to the Kim-Trump promise and eventual denuclearization.

That may be in response to growing frustration -- especially on the US side -- with the lack of progress in denuclearization since the Singapore summit. The delay in the work to retrieve the remains of American soldiers killed during the 1950-53 Korean War has also raised skepticism about the North’s attitude.

The North’s inaction encouraged some US congressmen and experts to call on strengthening of sanctions against the Kim regime and reconsider the decision to call off South Korea-US joint military exercises.

While the North Korean work to dismantle part of the missile test site is a positive development, it alone should not lead to excessive optimism as the North seems to not have departed from its usual tactic.

One good example is that the North’s state media resumed verbal attacks on the South Korean government of President Moon Jae-in. It did not mention Moon’s name, but made it clear that it was addressing him by finding fault with Moon’s recent comment that the international community would give a stern judgement if Kim or Trump did not keep the promise they made in Singapore. The North’s media called Moon’s comment “worthless advice” and accused him of “wagging his tongue.”

The sudden change of the North’s position on the Seoul government shows that the Kim regime still sticks to its usual negotiation tactics that include abrupt about-faces, disruptions and brinksmanship.

It was timely in that regard that the US government issued an advisory to warn businesses about violations of the UN- and US-imposed sanctions against the North.

The risks highlighted by the advisory included the “inadvertent sourcing” of goods, services, or technology from North Korea and ”the presence of North Korean citizens or nationals” in companies’ supply chains, whose labor generates revenue for the North Korean government.“ The 17-page advisory included a list of 239 companies vulnerable to North Korean evasion of sanctions and a list of 42 countries in which North Korean workers are staying.

Although US officials made clear that the advisory does not constitute new sanctions, it may as well add pressure to the North and some other countries which have been showing signs of relaxing the punitive measures taken against the North’s nuclear and missile provocations.

That should serve as a warning to all members of the international community, not least countries like China and Russia, the North’s traditional allies, that there should be no letup in the sanctions unless the North takes substantial denuclearization actions. This principle should apply to South Korea too.