( Associated Press Writer ) - Japan said Tuesday it had shot down a ballistic missile in space high above the Pacific Ocean as part of joint efforts with the United States to erect a shield against a possible North Korean attack.
Japan tested the US-developed Standard Missile 3 (SM-3) interceptor from a warship in waters off Hawaii, becoming the first US ally to intercept a target using the system.
Defence Minister Shigeru Ishiba described the successful test as "extremely significant."
"We will continue to strive to increase the system's credibility," he told reporters, insisting the missile shield was worth the high cost.
"We can't talk about how much money should be spent when human lives are at stake."
Japan plans to spend a total of 127 billion yen (11.2 billion dollars) over the four years to March 2008 on missile defence using the US-developed Aegis combat system, according to the defence ministry.
The naval destroyer Kongou launched the SM-3 which, at 2212 GMT Monday, or 7:12am Tuesday in Japan, intercepted the missile fired from onshore earlier, the navy said in a statement.
Officials said the interception was made around 100 miles ( 160 kilometres) above the Pacific.
The test was "a major milestone in the growing cooperation between Japan and the US," Japanese Rear Admiral Katsutoshi Kawano and Lieutenant General Henry Obering, director of the US Missile Defense Agency, said in a joint statement.
Washington and Tokyo have been working jointly to erect a missile shield against possible attacks from North Korea, which fired a missile over Japan's main island and into the Pacific Ocean in 1998.
However the missile defence system could affect Japan's relations with its neighbours "by arousing suspicion in enemy countries," said Yoshikazu Sakamoto, professor emeritus of the University of Tokyo.
"With regards to North Korea, Japan needs to enhance efforts in diplomatic negotiations to seriously address Pyongyang's military threat," he said.
China offered a muted reaction to Japan's anti-missile test, saying only it hoped Tokyo's actions would be positive for peace and trust in Asia.
"We hope that the actions of Japan are beneficial to the peace and stability of the region and conducive to mutual trust of the countries in the region," China's foreign ministry spokesman Qin Gang told journalists.
But the test angered peace activists in Japan.
Missile defence tests "facilitate military unification of Japan and the United States" and defy Japan's pacifist constitution, said Koji Sugihara, a member of a civic group campaigning against nuclear and missile tests.
Japan plans to install the missile shield on four Aegis-equipped destroyers by March 2011, including the Kongou. The success of the SM-3 test paves the way for completion of Japan's missile defence involving missiles fired from warships and ground-based launchers.
If the SM-3 system fails to intercept its target in space, the second stage of the shield uses ground-based Patriot Advanced Capability 3 (PAC-3) missile interceptors to try to shoot it down.
Japan introduced its first PAC-3 missile launcher at the Iruma air force base north of Tokyo in March, one year ahead of schedule amid tense relations with North Korea which, in October last year, tested a nuclear device for the first time.
Japanese authorities aim to increase the number of locations equipped with the PAC-3 system to 14 by March 2011.