He suggested the meeting could happen in January or February and that the USA could continue to enforce the economic sanctions it imposed on North Korea over its weapons program.
U.S. President Donald Trump and North Korea's leader Kim Jong Un shake hands during the signing of a document after their summit at the Capella Hotel on Sentosa island in Singapore, June 12, 2018.
The developments come against a backdrop in which Mr. Trump and his advisers say they are hoping for a second summit with Mr. Kim to discuss progress - or the lack thereof - toward denuclearization.
Kim sharply raised tensions with nuclear and missile tests last year, but suddenly reached out to South Korea and the United States this year with a vague nuclear disarmament pledge.
The North Korea official "achieved a self-reliant military line and actively contributed to the modernization of North Korea's defense industry", Choe said. "Any denuclearization agreement would require North Korea to allow global inspectors to determine that these units are no longer armed with nuclear weapons", according to the report from Lewis and Schmerler.
Last year, the USA led a series of U.N. Security Council sanctions resolutions punishing the North for its tests of nuclear weapons and intercontinental ballistic missiles.
Despite the deadlock, Trump has said he and Kim are "getting along very well" and have a "good relationship". But Lewis and Schmerler said that in recent years North Korea had significantly expanded what appeared to be another missile base in Hoejung-ni.
Washington and Pyongyang had been locked in a diplomatic standoff for weeks over which side would make concessions first.
"This is one of the important locations in North Korea our military is monitoring in cooperation with the United States", Roh Jae-cheon, a South Korean military spokesman, said Thursday about the North Korean base.
One such facility is the missile base near Yeongjeo-dong, a site that has long concerned US and South Korean officials and the subject of the analysis of the new images released Wednesday. Additional tunnels were also found, as seen in satellite pictures, including a pair of large drive-through shelters capable of holding large ballistic missiles.