The Japanese and US governments plan to extend their bilateral security treaty to apply to attacks in outer space.
Both sides are making arrangements for Article Five of the Japan-US Security Treaty to include space. The article obliges the United States to defend territories under Japan's administrative control.
The move comes as Japan faces the challenge of establishing a defense system in space. China and Russia are accelerating space technology to secure military advantages.
There are no borders in outer space, but Japan and the US are considering defining Japan's satellites as under the country's administration.
Both governments are expected to confirm the plan at a two-plus-two meeting of their foreign and defense ministers in Washington to be held on Wednesday, local time.
Japan and the US confirmed at a 2019 two-plus-two meeting that their security treaty also applies to cyberattacks.