The Beyond Parallel program at the Center for Strategic and International Studies identified the bases in a Monday report, signaling that Pyongyang has been misleading the West about its intentions to dismantle its missile program, according to The New York Times.
New analysis of satellite images suggest that, despite promises to the contrary, North Korea may be continuing to develop its nuclear missile program rather than dismantling it.
Fox News notes that the report comes as denuclearization talks between the USA and North Korea have stalled-Secretary of State Mike Pompeo's planned meeting with his North Korean counterpart last week was delayed indefinitely.
The existence of the bases does not represent a violation of the agreement Kim made with Trump at the summit, which involved vaguely-worded pledges on the "denuclearisation of the Korean peninsula", which Pyongyang interprets as a gradual, staged and reciprocal process of disarmament.
Cha had been in line for appointment as United States ambassador to South Korea, but was dropped because of disagreement with the Trump administration's approach.
The size of the entrances, as well as the volume of soil removed, indicates the base could house a brigade-size missile unit with up to 18 mobile launchers, the report said. "The United States remains focused on fulfilling the commitments agreed to by President Trump and Chairman Kim at the Singapore Summit in June".
"The fact that North Korea has continued to build nuclear weapons and ballistic missiles in the midst of high-level diplomacy with China, South Korea, and the United States should not come as a surprise", said Abraham Denmark, the Asia program director at The Wilson Centre.
"President Trump is getting played by Kim Jong Un", Edward J. Markey, a Democrat of MA and a member of the Foreign Relations Committee, said in a statement released Monday after the publication of the CSIS report.
"North Korea has never promised to shut down this missile base", Kim Eui-kyeom said in a statement, citing one base described in detail by the CSIS researchers.
The report identified about 15 to 20 bases being operated by the Korean People's Army's Strategic Force, based on information from officials in the government, defense and intelligence, as well as North Korean defectors.
But despite Trump's description of progress, North Korea has repeatedly lashed out at the US and threatened to resume building up its "nuclear forces".
The Sakkanmol base is about 80 km from the demilitarized zone, and from there the North launched two Scud or Rodong missiles in March 2016, three in July, and three in September into the East Sea.
USA analysts said Monday they have located 13 secret North Korean missile development sites, underscoring the challenge that the Trump administration faces in trying to reach its promised broad arms control agreement with Pyongyang.
In this file photo taken on June 11, 2018 North Korea's leader Kim Jong Un (R) walks with US President Donald Trump (L) during a break in talks at their historic US-North Korea summit, at the Capella Hotel on Sentosa island in Singapore.
The report was released less than a week after North Korea abruptly called off a new round of negotiations with Mr Pompeo that had been set for Thursday in NY.
None of the missile bases have 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 imagery shows barely visible entrances to seven underground facilities at the Sakkanmol missile base - each protected from artillery fire and air strikes by 60-foot-high (18-meter) berms made from rock and dirt excavated from the site.