The U.S. State Department has approved a proposed $821 million sale of SM-2 Block IIIB Standard Missiles to Japan.

The Defense Security Cooperation Agency, which oversees the U.S. Foreign Military Sales program, notified Congress of the possible sale on Friday, the agency said in a statement Tuesday.

Tokyo requested up to 246 of the SM-2 Block IIIB Vertical Launching Tactical All-Up Rounds, RIM-66M-09, the agency said.

The request would also include MK 13 MOD 0 Vertical Launching System Canisters, operator manuals and technical documentation, U.S. government and contractor engineering, and technical and logistical support services.

As a major political and economic player in East Asia and the West Pacific, it is vital to U.S. interests that Japan develop and maintain a strong and ready self-defense capability, the agency said.

The missile will be used for anti-air warfare at sea.

Japan now fields four Kongo-class and two Atago-class destroyers, which are equipped with the Aegis combat system and SM-2 missiles.

The country is also building two new Aegis-equipped destroyers based on a modified Atago-class hull, the agency said.

The missiles from this sale would be used on those future ships as well as to supplement Japan's inventory.

Principal contractors are Raytheon and BAE Systems.