TAIPEI, Taiwan — The US State Department has approved an $821 million sale of 246 Standard Missile-2 (SM-2) air defense missiles for deployment on Japan's four Kongo-class and two Atago-class destroyers.

The announcement was made July 19 by the US Defense Security Cooperation Agency (DSCA), which administers foreign military sales programs. The principal contractors will be Raytheon and BAE. There are no offset agreements with this sale.

The missiles are Raytheon-built RIM-66M-09 SM-2 Block IIIB vertical launching tactical all-up rounds. The deal also includes MK 13 MOD O vertical launching system canisters.

"Combined with the Aegis combat system, the SM-2 Block IIIB provides significantly enhanced area defense capabilities over critical East Asian and Western Pacific air and sea-lines of communication," a DSCA news release said. "Japan has two Intermediate-Level Maintenance Facilities capable of maintaining the SM-2 Block IIIB and will have no difficulty absorbing these new missiles into its armed forces."

Japan is also building two new Aegis-equipped destroyers based on a modified Atago-class hull, and the Block IIIBs will be used on these destroyers as well as supplementing Japan's missile inventory.

Japan has been building up its air defense capabilities in reaction to both North Korea's missile and nuclear weapons modernization efforts, as well as China's increasing efforts to dominate the East China Sea and challenge Tokyo's administration of the Senkaku Islands.

Part of this effort to counter the ballistic missile threat has been Japan's acquisition of the SM-3 Block 1A, which is capable of shooting down an oncoming missile in space. According to Raytheon news releases, Japan has conducted three successful SM-3 tests at the U.S. Navy's Pacific Missile Range Facility on Kauai, Hawaii.  The tests, conducted in 2007, 2009 and 2010, launched from Japanese destroyers and intercepted a medium-range ballistic missile at ranges of 60-100 miles above the Pacific Ocean.

"Japan is one of the major political and economic powers in East Asia and the Western Pacific, a key democratic partner of the United States in ensuring regional peace and stability, a close coalition ally in regional contingency operations, and a close cooperative and international exchange agreement partner," the July 19 DSCA news release said. "This transaction is consistent with U.S. foreign policy and national security objectives and the 1960 Treaty of Mutual Cooperation and Security."