WASHINGTON (AP) -- New satellite imagery shows North Korea is conducting major new construction to expand facilities at a launch site where it fired a rocket into orbit last December, a U.S. research institute said Friday.
The work at the west coast site of Sohae, near the northern border with China, includes what could be a new launch pad for testing mobile ballistic missiles.
The U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies stressed that's a preliminary analysis, based on scrutiny of commercial satellite imagery, the latest taken last Sunday.
The analysis was provided to the Associated Press ahead of publication on Friday by the institute's website, 38 North.
The construction includes upgrading of roads and other facilities.
Among those facilities is a compound likely used by troops involved in the building work.
An 11-car freight train is parked at a siding nearby.
The work began in midyear, and there are unlikely to be rocket launches at Sohae for the next six months while it is underway, the institute said.
Its assessment includes analysis by Nick Hansen, a retired intelligence expert who closely monitors developments in the North Korea's weapons programs.