One of tennis' four Grand Slams and the crown jewel of the U.S. tennis calendar, the U.S. Open usually attracts the world's greatest players to Flushing Meadows every year.

This year, however, several of the sport's top athletes have dropped out of the 2020 campaign, including defending champions Bianca Andreescu and Rafa Nadal, and world number 1 Ash Barty and fellow Australian Nick Kyrgios.

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Mike Dowse, CEO and executive director of the USTA, said the field "exceeded our expectations," given the challenges of putting on the event.

"In context of the times and how different the world is, I couldn't be happier," said Dowse.

Dowse said that the women's competition will see 10 former Grand Slam champions, including 23-time major winner Serena Williams, along with 81 of the top 100. In the men's event, seven of the world top ten are competing.

After winning the Prague Open, world number 2 Simona Halep became the latest big-name competitor to back out of the tournament on Monday, citing concern over travelling to New York amid the coronavirus pandemic.

The hard court tournament, which begins Aug. 31, will be held without fans and with safety measures in place to mitigate the risks associated with playing in the COVID-19 era. The Western & Southern Open, which usually takes place in Cincinnati, Ohio, will play out starting this week in New York.

Organisers said approximately 90% of players are already in town or in the tournament bubble.

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