Japan now has a two-layer missile shield: a ship-based Aegis system aimed at stopping short and intermediate-range ballistic missiles mid-flight, and ground-based PAC-3 interceptors to destroy warheads in their final stages of flight.
Aegis Ashore is a land-based version of the Aegis combat system developed for warships, a collection of radars, computers and missiles.
"North Korea's nuclear missile development poses a new level of threat to Japan and as we have done in the past we will ensure that we are able to defend ourselves with a drastic improvement in ballistic missile defence", Itsunori Onodera, the defence minister, said.
Japan's Cabinet on Tuesday approved a plan to purchase a set of costly land-based USA missile combat systems to increase the country's defence capabilities amid escalating threats from North Korea.
Initially, it was supposed to pay about 80 billion yen (almost $ 705 million) for one Aegis Ashore complex.
Japan already has two layers of missile defenses, including Aegis-equipped ships and land-based Patriot batteries.
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The Japanese government will request $6.5 million in next year's budget to conduct a geological survey ahead of the system's deployment.
Officials with the Russian Ministry for Foreign Affairs called the deployment of U.S. missile defense systems in Japan a violation of the treaty between the USSR and the United States, while Tokyo facilitates the initiative, Mikhail Ulyanov, Director of the Department for Nonproliferation and Arms Control at the Russian Foreign Ministry said.
Japan's military planners also evaluated the USA -built THAAD (Terminal High Altitude Area Defense) system before deciding on Aegis Ashore.
As the acquisition plan was not stated in the latest national defense policy guidelines drawn up in late 2013, the government chose to seek Cabinet approval for the decision, according to the officials. The United States developed the system and it has already been deployed by USA forces in Romania and Poland.
The Aegis Ashore batteries will be armed with SM-3 Block IIA and SM-6 interceptors.
North Korea has fired two missiles over Japan this year, as well as three intercontinental ballistic missiles on steep trajectories into the Sea of Japan.