The 21-year-old world number three is a dual citizen of Japan and the United States but is obliged to pick one country under Japanese law by her next birthday.

According to NHK, she has opted for Japan, with the double grand slam winner set to turn 22 on Wednesday (October 16).

Osaka has represented Japan throughout her career, including at the Fed Cup, and has previously targeted playing at a home Olympics.

She will be a huge host-nation hope for gold in the Tokyo 2020 tennis tournament at Ariake Tennis Park.

Born in Osaka, the former world number one has parents from Japan and Haiti.

She grew up in the United States and won her first grand slam at the US Open last year, before making it two at this year's Australian Open.

Osaka is currently in fine form, winning the Toray Pan Pacific event in September and the China Open this month. 

In July, in an interview with the International Tennis Federation, she said: "Winning gold in Tokyo is something that I have dreamed about.

"It would be the biggest thing I would have achieved in my career, although in some ways that is simply because of timing.

"I contest grand slams every year, but an Olympic Games is only once every four years so there are not many opportunities to become an Olympic champion.

"Everyone who competes at the Olympics wants to be an Olympic champion, so that would be my aim."