They suggest Pyongyang is continuing its missile work, even though it has halted test launches in what President Donald Trump and his Government have claimed as a success since his historic June meeting with North Korean leader Kim Jong-un in Singapore.
The Center for Strategic and International Studies, relying on satellite images, defector testimony, and interviews with defence and intelligence officials, has discovered 13 of an estimated 20 possible secret ballistic missile bases hidden in the mountains of North Korea.
The CIA declined to comment on the images, but United States officials have expressed concern about North Korea using hidden and undeclared locations to continue to work on improving their missile technology and possibly their nuclear program.
However, plans for a second meeting could be in jeopardy after leading regime figure Kim Yong-chol failed to turn up for a meeting in NY with US Secretary of State Mike Pompeo. "As of November 2018, the base is active and being reasonably well-maintained by North Korean standards", the report noted.
The sense of skepticism is expected to increase, as Democrats who took over the House of Representatives are ratcheting up their criticism of Trump's approach toward North Korea and his idea of holding a second summit with Kim.
He has said sanctions would stay in place until North Korea disarmed, but that he was "no rush" to force the pace of disarmament. "While missiles could be launched from within them in an emergency, Korean People's Army (KPA) operational procedures call for missile launchers to disperse from the bases to pre-surveyed or semi-prepared launch sites for operations".
Many North Korea watchers doubt that the regime will ever truly give up nuclear weapons, to which three generations of the Kim dynasty have generously devoted the country's scarce resources.
A month later, experts said North Korea had stopped dismantling a different rocket test site, also based on satellite photographs taken at the time and other sources.More news: Twitter reacts as Real Betis beat Barcelona 4-3
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"The base can be functionally divided into four activities - agricultural support [including numerous greenhouses dispersed throughout the facility], main base [including headquarters, barracks, missile support, vehicle maintenance, storage, and a variety of small support elements], and underground and missile support facilities", the analysts said.
The Korean Marine Exchange Program (KMEP) violated a Sept 19 agreement signed by North and South Korea that called for a halt to "all hostile acts", said the Rodong Sinmun, North Korea's official party newspaper.
Report co-author Joseph Bermudez Jr asserted: "The level of effort that North Korea has invested in building these bases and dispensing them is impressive".
Recently, North Korea has demanded that the United States end its tough economic sanctions now that it is negotiating with Trump over its nuclear program.
None of the missile bases has been acknowledged by North Korea and analysts say an accurate disclosure of nuclear weapons and missile capabilities would be an important part of any denuclearization deal.
The day after the summit, Trump wrote on Twitter that there was "no longer a nuclear threat from North Korea".
Analysts have long believed that North Korea had undeclared or hidden facilities in their missile programme, which has made issues related to verification and inspections a major part of working level talks between the USA and North Korea.