"I am so disappointed to have to announce that I tested positive for covid and can not play during the Olympic Games in Tokyo.
It has always been a dream for me to represent the USA at the Olympics and I hope that there will be many more chances for me for it to become real in the future ", she writes on Twitter.
The 25-ranked American is the latest in a series of stars who do not come to play in Tokyo.
Roger Federer, Rafael Nadal, Dominic Thiem, Serena Williams, Simona Halep and Bianca Andreescu, among others, have previously refused.
However, world number one Djokovic has announced that he will play in the Olympics.