The United States has approved a planned sale of two Aegis weapon systems and related equipment to Japan for an estimated cost of $2.15 billion, the State Department said Tuesday.

The planned sale involves the land-based Aegis Ashore missile defense system, which Japan is considering setting up in two locations -- Akita and Yamaguchi prefectures -- in fiscal 2023 to counter the North Korean missile threat, according to U.S. officials.

The sale "will provide the government of Japan with an enhanced capability against increasingly sophisticated ballistic missile threats and create an expanded, layered defense of its homeland," the department said.

"It is vital to U.S. national interests to assist Japan in developing and maintaining a strong and effective self-defense capability," it said.

The U.S. Defense Security Cooperation Agency notified Congress of the arms deal on Tuesday.

The move comes as Russia has repeatedly expressed concerns about Japan's planned deployment of two Aegis Ashore stations.

Moscow, which has been engaging in negotiations with Tokyo for a postwar peace treaty, regards them as an addition to the U.S. missile shield in the Asia-Pacific region.

The State Department sought to allay such concerns, saying, "The proposed sale of this equipment and support does not alter the basic military balance in the region."

Since Japan possesses Aegis-equipped destroyers in its inventory, Tokyo will have no difficulty in absorbing the envisaged systems into the Self-Defense Forces, according to the department.

The Japanese government has requested the purchase of two Aegis weapon systems, two multi-mission signal processors, two command and control processor refreshes, as well as related equipment and services, it said.

Japanese defense officials have said the planned deployment of the Aegis Ashore systems is "purely for national defense."