WASHINGTON – North Korea has at least 13 secret operating bases where the regime is continuing work on its ballistic missile program, a sign Kim Jong Un is not winding down his country’s nuclear program despite public promises touted by the Trump administration.

New research, conducted by the Washington-based Center for Strategic and International Security, has identified 13 of an estimated 20 North Korean missile operating bases that Kim's regime has not declared.

North Korea's highly publicized move to decommission a satellite launch facility gained a flurry of positive media attention. But that move "obscures the military threat to U.S. forces and South Korea from this and other undeclared ballistic missile bases," the CSIS report concludes.

A State Department spokesperson did not address the new findings, but said: “President Trump has made clear that should Chairman Kim follow through on his commitments –including complete denuclearization and the elimination of ballistic missile programs – a much brighter future lies ahead for North Korea and its people.”

South Korean officials downplayed the report’s claims on Tuesday, saying that they were nothing new to the intelligence communities in Washington or Seoul.

A spokesman for South Korean president’s office, Kim Eui-kyeom, said that the information about a missile base profiled by CSIS was taken from commercial satellite imagery and that state intelligence agencies already had more in-depth information.

"The U.S. already knows in much more detail using military satellites," Kim said. “And [South Korea is] watching closely, but there is nothing new.”

Undeclared North Korea: Missile Operating Bases Revealed - Beyond Parallel

Kim also said that the base, called Sakkanmol, was used for short-range missiles only, not intercontinental ballistic missiles (ICBMs), and that no agreement to dismantle it had been negotiated.

“I do not think it is appropriate to call this a ‘deception’,” Kim said. “I think it further emphasizes the need for negotiations and dialogue, including North American dialogue, to get rid of these North Korean threats.”

CSIS experts used satellite images to locate the undeclared military bases, which they said could be used "for all classes" of ballistic missiles, including intercontinental missiles capable of reaching the United States.

The findings, first reported by the New York Times, stand in stark contrast to President Donald Trump's declaration that North Korea no longer represents a nuclear threat and that he has made progress is persuading Kim to declare and relinquish his nuclear arsenal.

The new report emphasizes that the hidden bases are not launch facilities. However, they are "permanent facilities that contain a unit’s headquarters, barracks, housing, support, maintenance, and storage facilities," the report says.

Trump claimed in June that "there is no longer a nuclear threat" from North Korea just after he returned to the U.S. from a historic summit meeting with Kim in Signapore.

"Everybody can now feel much safer," Trump tweeted about that meeting with the North Korean dictator. Critics have derided Trump's claims.

"This idea that they’re giving up their nuclear program is quite a fantasy," said Ivan Eland, a national security expert with the Independent Institute, a Libertarian-leaning think tank.

He and others said revelation that North Korea has continued unabated with its ballistic missile program is no surprise.

"Kim literally ordered ballistic missiles to be mass produced on New Year’s day 2018," Vipin Narang, a professor MIT and expert in nuclear proliferation, said in a tweet on Monday. "He never offered to stop producing them, let alone give them up. Ever. He is doing exactly what he said he was going to do.

At the Singapore summit, Trump and Kim signed a vaguely worded agreement in which North Korea promised to work toward a “complete denuclearization of the Korean Peninsula.” But the North Koreans have not few visible, concrete steps toward fulfilling that pledge.

North Korea has not, for example, provided the U.S. with a detailed list of its nuclear arsenal – which Secretary of State Mike Pompeo and other U.S. officials see as a vital first step toward denuclearization.

"Trump just got fleeced at the summit," Eland said.

Trump and Kim have agreed to hold a second summit, possibly early next year. But the planning for that meeting seems to have stalled.

More:Day after summit, Trump claims North Korea 'no longer a nuclear threat'

More:Secretary of State Mike Pompeo touts progress, with few details, after Kim Jong Un meeting

More:President Trump says easing sanctions on North Korea is a 'two-way street'

Contributing: Thomas Maresca from Seoul.