Naomi Osaka says rising Covid-19 levels in Tokyo are a "big cause for concern" and she is "not really sure" the Olympics should go ahead this summer.
Tokyo is under a state of emergency amid a surge in cases, 10 weeks from the start of the rescheduled Games on 23 July.
Japanese world number two Osaka would be making her Olympic debut in Tokyo.
"I'm an athlete, and of course my immediate thought is that I want to play in the Olympics," she said.
"But as a human, I would say we're in a pandemic, and if people aren't healthy, and if they're not feeling safe, then it's definitely a really big cause for concern.