A rocket takes off from a North Korean launch site.
Smoke rises during a rocket firing drill of the strategic force of the Korean People's Army in this undated photo released by North Korea's Korean Central News Agency in Pyongyang, July 27, 2014. Reuters/KCNA

North Korea is about to finish upgrades to an aging satellite launch station that will eventually be capable of firing rockets that could be used to carry nuclear warheads, a Washington, D.C.-based think tank that focuses on political and military developments in North Korea reported Friday. Satellite imagery shows new additions to the Sohae launch site, including construction of fuel and oxidizer propellant storage bunkers, according to 38 North, a website run by the John Hopkins University School of Advanced International Studies.

“That program is probably designed to support future activities related to the testing and launching of larger rockets,” a 38 North statement said, noting that the site could be up and running by early next year. “With the upgrade program nearing completion, North Korea will be ready to conduct further activities at Sohae — including space launches — by the first quarter of 2016, should the leadership in Pyongyang decide to do so.”

The facility, which dates back to the early 1990s, will eventually be capable of firing rockets that are around 60 meters long, twice the size of the Unha-3 rocket that enabled North Korea to put a satellite in space in December 2012, according to a Friday report by Stars and Stripes. North Korean officials claimed that its rockets were capable of reaching the U.S. mainland, but there has been no independent verification of that claim.

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On Thursday, North Korea leader Kim Jong Un said that the country was now equipped with hydrogen bombs, which are hundreds of times more powerful than atomic bombs, although there is skepticism over Pyongyang’s ability to build a thermonuclear bomb that requires advanced scientific techniques.

"Kim has revealed on a number of occasions that North Korea possesses nuclear bombs. But this appears to be the first time that he talked about an H-bomb," Chang Yong-seok, a researcher at the Seoul National University Institute for Peace and Unification Studies, told Yonhap, a South Korean news group.

U.S. sanctioned Pyongyang’s strategic rocket force group Tuesday, blacklisting six individuals, two banks and three shipping firms that are believed to be involved in the arms trade.

“North Korea threatens international peace and security by expanding its nuclear program and continuing its proliferation of weapons of mass destruction and conventional weapons,” Adam J. Szubin, acting undersecretary for Terrorism and Financial Intelligence, said in a statement, according to a BBC news report Wednesday. “[The Treasury Department] is committed to exposing North Korea’s global proliferation network and excluding these facilitators from the international financial system.”