The government also authorized the use of U.S. SM-3 interceptor missiles as part of Japan's two-layer missile shield, following a successful test of the missile earlier in December.
Japan's determination to boost its missile defenses was strengthened after North Korea conducted a series of ballistic missile tests in July 2006, and an underground nuclear test explosion three months later.
Under a December 2004 missile defense cooperation arrangement with the U.S., Japan is planning to build by 2011 a missile-defense network comprising sea- and land-based components.
The U.S. sea-based SM-3 interceptor missiles are designed to intercept incoming ballistic missiles in mid-trajectory at altitudes up to 300 kilometers (about 190 miles), while land-based U.S. Patriot PAC-3 systems, which will be deployed at four ground-to-air missile units, are expected to shoot down missiles before they hit the ground.
During a test-launch on December 17 from the Japanese Aegis-equipped destroyer Kongou, an SM-3 interceptor shot down a simulated target over the Pacific near Hawaii.
Commander of Japan's Maritime Self-Defense Force (MSDF) Eiji Yoshuikawa said at the time that the success of the test would mean that Japan "could be able to destroy foreign missiles by the end of the year."
Japan may arm four of its Aegis-equipped destroyers with SM-3 interceptor missiles by March 2011.
Tokyo and Washington are planning to conduct in January 2008 their first joint exercises on countering a potential missile attack.