The U.S. military deployed a mobile missile-tracking system in northern Japan on Friday as part of a joint defense pact to protect against the missile threat from North Korea, Japanese defense officials said.

The Joint Tactical Ground Station, a mobile station that can detect and analyze satellite data on ballistic missile launches, arrived at Misawa Air Force Base in Aomori prefecture (state), a Defense Ministry spokeswoman said on condition of anonymity, citing ministry protocol.

It is the first mobile U.S. missile tracking system to be deployed in Japan.

Another ministry official, also talking on condition of anonymity, refused to say when the tracking system would come into operation, citing security.

The mobile missile-tracking system is designed to receive launch data from early warning satellites, analyze the projected destination of missiles and forward the information to the U.S. military and Japan's Defense Ministry.

Tokyo and Washington have been jointly developing an advanced missile defense system and also have stepped up joint missile defense programs since North Korea's missile launches and nuclear test last year.

Japan will conduct its first missile test in mid-December, from an Aegis-radar equipped destroyer off Hawaii, "to confirm its ballistic missile defense capability," the Defense Ministry said separately in a statement.

Japan deployed its first advanced U.S.-developed Patriot missiles earlier this year, and plans to introduce SM-3 interceptors on its destroyers in the next few years, including one in December.

The two countries held a regional ballistic missile defense drill in July. Another round of exercises is scheduled for November, followed by a test launch of the U.S.-developed SM-3 missile interceptor from Japan's Aegis-class destroyer Kongo during the week of Dec. 17 off a Hawaiian island of Kauai, the ministry said.

The U.S. keeps about 50,000 troops across Japan under the bilateral security pact.