New satellite imagery released by the Center for Strategic and International Studies shows the Sakkanmol Missile Operating Base, one of more than a dozen locations where North Korea continues to develop ballistic missiles.
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.
Japan, which has called on the worldwide community to maintain pressure on Pyongyang, is supportive of the United States' latest stance on the annual military drills that Trump indefinitely suspended following his first-ever summit with North Korean leader Kim Jong Un in mid-June in Singapore.
Pompeo and other USA officials have said that clearly includes dismantling its entire nuclear weapons program, but North Korea has not confirmed that.
An official with South Korea's Joint Chiefs of Staff also told reporters that Seoul is "familiar" with the sites identified in the report but declined to confirm whether intelligence had indicated any recent changes at the bases.
The Trump administration has touched on the possibility of resuming the two major spring exercises with South Korea known as Key Resolve and Foal Eagle, the sources said.
The quiet continual operation of Sakkanmol and other sites flies in the face of what the Trump administration says is a pledge by North Korea to dismantle its nuclear weapons program.
The day after the summit, Trump wrote on Twitter that there was "no longer a nuclear threat from North Korea".
"Our government will participate in the adoption of the resolution under the basic principle to make joint efforts with the global community for the human rights of North Korean people to be addressed substantively as a universal value of mankind", Kim said at a press briefing.
Under an agreement made between their generals in late October, North and South Korea agreed to each remove 10 posts and preserve one on either side of the frontier.
Bases for strategic weapons such as intercontinental ballistic missiles - whose development is the subject of sanctions - are located deep inside the country.
Within the Japanese government, many believe that North Korea will not completely abandon its nuclear ambitions if the United States does not exert strong pressure on Pyongyang.
Indeed, it appears to be adding to its stockpile: U.S. intelligence reports from the northern summer found that North Korea had begun producing new missiles at a factory, and Secretary of State Mike Pompeo acknowledged during Senate testimony that Pyongyang "continues to produce fissile material".
'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'.
The Centre for Strategic and International Studies (CSIS) thinktank in Washington however has published satellite photographs of a short-range ballistic missile operating base near the demilitarized zone (DMZ) capable of accommodating medium-range missiles and threatening United States forces in the region.
"We've made incredible progress - beyond incredible".