The U.S. military has activated a high-powered radar outpost in northern Japan capable of tracking ballistic missiles, a key part of a joint missile defense project, amid concerns about North Korea and its nuclear ambitions.

U.S. Brig. Gen. John E. Seward hosted a ceremony Tuesday at Camp Shariki in Aomori Prefecture to activate the unit operating the X-band radar, U.S. Army Japan press officer Maj. Martha Brooks said Thursday.

The high-resolution radar can identify flying objects the size of a baseball from thousands of kilometers away and can differentiate between decoys and real warheads. Japan and the United States began working on the project after North Korea fired a long-range missile over Japan in 1998.

It is part of a sweeping, multibillion dollar defense shield that includes joint production of new missiles capable of intercepting and destroying incoming missiles and the deployment of advanced Patriot interceptor missiles around Japan.

Japan is well within range of North Korean missiles and has been deeply disturbed by Pyongyang's claim to possessing nuclear weapons and its test-firing of seven missiles in July, including a long-range missile believed capable of reaching North America.

The radar installation was relocated to its present site from Misawa Air Base, also in Aomori Prefecture.

Brooks declined to say if the X-band radar was redeployed to keep a better eye on North Korea, but said, "we're here in defense of Japan, and they put it in a location where they could best track the ballistic missiles."

The U.S. military in Japan released a statement saying the installation is "a defensive system with no offensive capability."

Japan and the United States say North Korea's Taepodong-2 missiles have an estimated range of 15,000 km, potentially capable of reaching the U.S. mainland.