The images, obtained by CNN, offer evidence that the Yeongjeo-dong missile base and a nearby, previously unreported, site remain active and have been continually upgraded, highlighting the continuing gulf between Pyongyang and Washington's views on denuclearization.
In a report published last month, a Washington-based research institution, the Center for Strategic and International Studies, said it had located more than a dozen North Korean missile bases still in operation.
North Korean efforts to upgrade and expand a long-range missile base come as no surprise to US intelligence officials, who have always been wary of promises by Pyongyang to denuclearize.
The images indicate that North Korea was building an extremely large underground facility in 2017 and that this facility was still under construction as of August 2018.
"Any denuclearization agreement would require North Korea to allow global inspectors to determine that these units are no longer armed with nuclear weapons", they said.
North Korea has clandestinely expanded one of its main long-range missile development bases during recent months, according to new reports based on satellite imagery collected during October and November.
Officials from the Pentagon and the State Department told CNN that they could not discuss matters related to national intelligence.
But the North has rejected demands for what it calls "unilateral" disarmament, and has instead sought unspecified reciprocal U.S. measures in a gradual process.
-North Korea negotiations to dismantle Pyongyang's nuclear weapons program.
But diplomacy has since come to a halt amid disputes over a USA demand that North Korea first produce a full inventory of its nuclear weapons and take other denuclearisation steps before winning significant outside rewards. On Saturday, he told reporters that his next meeting with Kim was likely to happen in January or February. That includes missiles capable of reaching not just California, but anywhere in the United States.
The two men met in Singapore in June and signed a vaguely worded document that pledged to "work toward" the complete denuclearization of the Korean peninsula, though it did not detail specifics on how this would come about. "Any denuclearization agreement would require North Korea to allow worldwide inspectors to determine that these units are no longer armed with nuclear weapons", according to the report from Lewis and Schmerler.
The base itself is strung along a narrow valley.