USA analysts say they have located more than half of an estimated 20 secret North Korean missile development facilities.
Writing for the Center for Strategic and International Studies' Beyond Parallel initiative on Korean issues, analysts Joseph Bermudez, Victor Cha and Lisa Collins said the Sakkanmol Missile Operating Base in North Hwanghae Province show signs of use.
Photo An overview of the Sakkanmol Missile Operating Base and adjacent unidentified military facility.
That dismantling started and then stalled, and the new images show serious subterfuge was underway.
Sakkanmol and other similar bases represent the backbone of North Korea's nuclear defense.
The country has failed to take even the first step towards denuclearisation - providing a list of existing sites.
North Korean leader Kim Jong Un attends the joint press conference with South Korean President Moon Jae-in at Paekhwawon State Guesthouse on September 19, 2018 in Pyongyang, North Korea. Now it's North Korea's turn. "While missiles could be launched from within them in an emergency, Korean People's Army operational procedures call for missile launchers to disperse from the bases to pre-surveyed or semi-prepared launch sites for operations".
Bermudez began studying the North Korean ballistic missile infrastructure in 1985.
While no clear reason was given for why the sudden scheduling conflict, the USA and South Korea tried to quell concerns and said the talks would be rescheduled shortly.
This information is a setback for President Trump, who in recent months has boasted about the progress made after his summit with Kim in Singapore on June 12, which led, among other gestures, to the decommissioning of the Sohae missile base, in the northwest of the country in July.
After the summit, Kim Jong-un vowed to "work towards complete denuclearisation of the Korean peninsula" and the United States subsequently cancelled planned military drills with South Korea.
But President Trump continues to boast about the success of USA efforts, saying as recently as last week that North Korea had halted missile tests and returned American hostages.
Since the summit in Singapore, North Korea has forgone nuclear and missile tests, dismantled a missile test site and promised to also break up the country's main nuclear complex if the U.S. makes concessions.
But South Korea has defended the exercises.
On Wednesday, after his party lost control of the House of Representatives, Mr Trump reiterated: "The sanctions are on".
North Korea declared its nuclear force "complete" and halted missile and nuclear bomb testing earlier this year, but US and South Korean negotiators have yet to elicit from Pyongyang a concrete declaration of the size or scope of the weapons programs, or a promise to stop deploying its existing arsenal.
No clear explanation was given, but Pyongyang is demanding sanctions imposed on it over its weapons programmes are eased while the Washington insists that they should stay in place until the North denuclearises.
But the South Korean government and analysts played down the report, saying that the facilities had been known about for years and Pyongyang had never offered to give them up.
"Missile operating bases are not launch facilities", the report said.
In North Korea, they are typically rudimentary structures with few large buildings, paved roads or security measures. "The base runs through a narrow mountain valley over an area of three square miles".
They nearly always consist of a network of underground facilities to house the unit's transporter-erector-launchers or mobile-erector-launchers, an inventory of missiles and warheads, and other technical or launch support vehicles and equipment. Some, like the base at Sakkanmol, house shorter-range missiles, while others house missiles capable of striking farther afield, including targets in Japan and the continental United States.