Ash Barty says she has withdrawn from the U.S. Open because she is not comfortable with traveling during the coronavirus pandemic.
Barty is the biggest name yet to opt out of the Aug. 31-Sept. 13 Grand Slam tournament in New York because of the global health crisis.
"I love both events so it was a difficult decision but there are still significant risks involved due to COVID-19 and I don't feel comfortable putting my team and I in that position.
"I wish the USTA all the best for the tournaments and look forward to being back in the U.S. next year."
The reigning French Open champion will decide later whether to defend her title at Roland Garros starting in late September.
"I will make my decision on the French Open and the surrounding WTA European tournaments in the coming weeks," she said.
Her decision came despite the New York area keeping coronavirus cases at a relatively low level since spiking in March and April while areas such as Florida, Texas and California have become hotspots.
There have been more than 4.4 million detected infections in America so far.
It was not unexpected from Barty, who last month expressed concerns about the US Open going ahead, and she won plenty of support Thursday on social media for her "sensible" decision to give it a miss.
The 24-year-old, who surged to the top of the rankings last year and has stayed there since, said she would continue to monitor the situation before deciding whether to travel to Europe to prepare for a defence of her French Open crown.
"I will make my decision on the French Open and the surrounding WTA European tournaments in the coming weeks," she said, with Roland Garros due to start on September 27.
(With inputs from Agencies)