The possible deal, which covers 98 of the Japan Air Self Defense Force's around 200 F-15Js, has an estimated value of $4.5 billion.
"This proposed sale will provide Japan a critical air defense capability to assist in defending the Japanese homeland and U.S. personnel stationed there.
Modernized F-15J assets will better enable Japan to respond to airborne threats and defend its airspace."
In addition, its notice says that Japan will source other unspecified items and services for this upgrade program via direct commercial sales with Japanese firm Mitsubishi Heavy Industries (MHI).
The improved radar on the F-15J JSI is likely to be used in conjunction with new air-to-air missiles in the future.