"At the vertical engine test stand, while significant progress in tearing down the facility was made from July to early August, no new dismantlement activity is apparent since August 3," according to Wednesday's article. "The components previously removed remain stacked on the ground."

Work on the launch pad also appears to have halted, it said, with the same parts that were previously removed still piled on the ground.

Dismantling the missile engine testing site was a verbal promise made by North Korean leader Kim Jong-un to US President Donald Trump at their landmark June summit in Singapore.

The two also reached a broad agreement that committed Kim to work toward "complete denuclearization" of the Korean Peninsula in exchange for security guarantees from the US.

Negotiations to implement the deal appear to have stalled as Washington demands to see verifiable steps toward denuclearization while Pyongyang insists on jointly declaring a formal end to the 1950-53 Korean War, which ended with an armistice.

"While activity at the site seems to have slowed down, there has only been a slight reduction in the number (from 11 to 7) of trucks and trailers at the Administrative and Security Headquarters," 38 North noted. "These vehicles appear to be related to the activities at the engine test stand and launch pad." (Yonhap)