Ashleigh Barty of Australia, the world No. 1 singles players in women's tennis, has withdrawn from the U.S. Open tennis grand slam event and its tune-up tournament Western & Southern Open, both will be played in New York later this year, over the concern of the COVID-19 pandemic.

"My team and I have decided that we won't be traveling to the U.S. and Western and Southern Open and the U.S. Open this year," Barty said in a statement issued by her manager on Thursday.

"I love both events so it was a difficult decision," she said. "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 United States Tennis Association (USTA) all the best for the tournaments and look forward to being back in the U.S. next year."

The 24-year-old Australian added that she would make a decision on the French Open and the surrounding Women's Tennis Association (WTA) European tournaments in the coming weeks.

Barty has joined world No. 2 Simona Halep of Romania, No. 6 Bianca Andreescu of Canada and No. 10 Naomi Osaka of Japan for not playing in the U.S. Open.

Djokovic, Nadal and Serena enter U.S. Open tune-up

The Western & Southern Open, which is normally held in Mason, Ohio, will serve as a tune-up tournament for the U.S, Open and also be held at the USTA Billie Jean King National Tennis Center in New York this year, organizers said on July 29.

The tune-up event will be staged August 20-28 and the U.S. Open main draw is set to begin on August 31 without spectators.

World's top two-ranked male players Novak Djokovic of Serbia and Rafael Nadal of Spain and women's tennis giant Serena Williams have all entered next month's Western & Southern Open.

Despite the fact that the U.S. has been seeing a daily rise in new COVID-19 cases, organizers said defending champions Daniil Medvedev of Russia and Madison Keys of the U.S. are also among the initial entries.

WTA world No. 3 Karolina Pliskova of the Czech Republic, No. 4 Sofia Kenin and No. 9 Serena Williams, both of the U.S., are listed as entrants headlining in the women's field that will feature 39 of the top 53 players in the world.

U.S. Open can't be a national championship, says Mouratoglou

Patrick Mouratoglou, the long-time French coach of Serena Williams, feels the U.S. Open must not turn into a national championship for the country and says organizers need to address players' health concerns by next week.

Concerns remain that players might have to undergo mandatory quarantine upon returning to Europe, forcing them to miss high-profile tournaments in Madrid and Rome ahead of the French Open at the end of September.

"If there is a quarantine it will mean that players cannot play Madrid and Rome," Mouratoglou said.

"But if they can't play Madrid and Rome and have to be quarantined that would mean they're sitting in an apartment for two weeks right before playing a grand slam on clay which sounds a bit crazy."

(With input from agencies)