Japan has deployed two missile defense detachments near Tokyo and plans major drills around its capital and its first sea-based interceptor test off Hawaii this month, underscoring its missile arms race with neighboring North Korea and China.

The moves cap a decade-long effort by Tokyo — with the strong backing of Washington — to erect the region's most advanced ballistic missile defenses.

Defense Ministry officials said Japan is installing its second "PAC-3" Patriot missile defense system at an air base just east of Tokyo. The first was set up west of Tokyo in March and nine more are to be readied around the country by March 2011.

The deployment comes as the Defense Ministry is planning to conduct anti-ballistic missile drills throughout the city, testing for communications obstacles or other problems in the surrounding areas.

The drills — the first of their kind — reportedly involve trucking missile launchers and troops from their bases on the outskirts of the city into several highly populated districts, including a shopping and entertainment area and a site near the Imperial Palace.

Japanese media have reported the drills will take place over the next month, but officials would confirm only that preparations are under way and the drills "should be held soon."

"We have yet to cover all of Japan, but will continue deployment beginning with key spots," chief Cabinet spokesman Nobutaka Machimura said Tuesday. "Missile defense is something we have been discussing and allocating budgets to for years as a major pillar of our national defense."

Defending Tokyo is of crucial importance to Japan because it is where roughly a quarter of the population lives, along with being the nation's political and economic center. But the detachments of PAC-3 missiles at the two bases outside the city are too far away should Japan's ship-based defenses fail — the missiles have a range of only 9-12 miles.

To test the longer-range sea-based shield, Japan is to conduct a missile intercept exercise from the Aegis destroyer Kongo off Hawaii around Dec. 17. The maneuver, following tracking simulations that have already been successfully completed, is to be held jointly with the U.S. Navy.

If successful, the event would be the first time Japan has ever intercepted a ballistic missile.

Japan will begin introducing Standard Missile-3 interceptors on its destroyers over the next few years, and five navy ships are already equipped with the Aegis ballistic missile tracking system.

Japan made ballistic missile defense a top priority after North Korea launched a long-range "Taepodong" missile over its main island in 1998.

Tokyo has since poured billions of dollars into its space defenses, launching a series of spy satellites, introducing the PAC-3s and regularly sending warships into the Sea of Japan to monitor North Korean activity.

The sense of urgency was heightened in October last year when North Korea conducted its first underground nuclear test explosion.

But concerns have recently also shifted to China, which earlier this year blasted an old weather satellite out of low-Earth orbit with a land-based missile, demonstrating its ability to take out military satellites that are crucial for modern battlefront communications.

Washington is also moving to strengthen its missile defenses in the region.

In February, the United States, which maintains about 50,000 troops throughout Japan, deployed an Army detachment of Patriot missiles at a base on the southern Japanese island of Okinawa, where most of the troops are based.

By 2009, the U.S. Navy plans to install ballistic missile tracking and interception capabilities on 18 cruisers and destroyers, 16 of which are assigned to the Pacific Fleet.

Many of those ships are in Japan. The largest U.S. Navy base outside of the United States is in Yokosuka, just south of Tokyo.

Japan's efforts to bolster its military, which operates under a pacifist constitution, are highly sensitive, and frequently prompt strong rebukes from China and North Korea. But government spokesman Machimura said he does not expect any major repercussions from its stepped-up missile deployments.

"I don't think there will be a major reaction," he said. "Every country is working hard for its defenses."