WASHINGTON (AP) — A U.S. research institute says North Korea has completed a year-long construction program enabling it to handle bigger rockets at its main launch site.

The U.S.-Korea Institute says Pyongyang could now conduct a launch from the Sohae site by year's end if it wants to.

There's no clear sign that a launch is in the works, but the analysis published Wednesday will deepen concern over North Korea's missile program.

North Korea conducted what it called a peaceful space launch from Sohae in December 2012, drawing international criticism. The U.S. is concerned the North is getting closer to having a missile that can reach America.

Sept. 13 satellite imagery shows Sohae's now-expanded launch tower getting a coat of anti-rust paint. There are new buildings and improved road and rail access.