Report: There are as many as 20 secret missile sites in North Korea

Researchers have found an undisclosed ballistic missile base in North Korea, and say there could be as many as 20 secret bases across the country.

Beyond Parallel, a project sponsored by the defense think tank Center for Strategic and International Studies, released a report on Monday that revealed the existence of the Sino-ri Missile Operating Base, 130 miles north of the DMZ. Satellite photos of the base taken in late December show an entrance to an underground bunker, hardened shelters, and the headquarters of the Korean People's Army Strategic Rocket Forces missile brigade. Beyond Parallel says the base has been crucial in the development of ballistic missiles able to reach Japan, South Korea, and Guam.

In February, the U.S. and North Korea will meet for a second nuclear summit, and one of the report's authors, Victor Cha, told NBC News the North Koreans are "not going to negotiate over things they don't disclose." Even if North Korea agreed to dismantle all nuclear facilities that have been disclosed to the United States, "they're still going to have all this operational capability," Cha added.