Defending champion Rafael Nadal won't compete at the US Open later this month.
He's pulled out due to the coronavirus pandemic - saying the situation is still "very complicated" around the world.
The competition begins on August 31 at Flushing Meadows in New York.
The tournament will be played behind closed doors, and with strict medical protocols in place.
However, Nadal tweeted on Tuesday evening to confirm he wouldn't be defending his title later this month.
This is a decision I never wanted to take but I have decided to follow my heart this time and for the time being I rather not travel. pic.twitter.com/8VA0aSACVy
— Rafa Nadal (@RafaelNadal) August 4, 2020
"After many thoughts I have decided not to play this year’s US Open," he wrote.
"The situation is very complicated worldwide, the COVID-19 cases are increasing, it looks like we still don’t have control of it.
"We know that the reduced tennis calendar is barbaric this year after 4 months stopped with no play, I understand and thank for the efforts they are putting in to make it happen.
"We have just seen the announcement of Madrid not being played this year.
"All my respects to the USTA, the US Open organisers and the ATP for trying to put the event together for the players and the fans around the world through TV.
"This is a decision I never wanted to take but I have decided to follow my heart this time and for the time being I rather not travel."
It means this year's US Open will be the first Grand Slam since 1999 to take place without both Roger Federer (injured) or Nadal.
Novak Djokovic has been included in the field for the US Open, but just six other members of the current ATP top 10 join him.
No. 3 Dominic Thiem, No. 5 Daniil Medvedev (a 2019 US Open finalist), No. 6 Stefanos Tsitsipas, No. 7 Alexander Zverev, No. 8 Matteo Berrettini and No. 10 David Goffin will all be at Flushing Meadows.
Nine of the women's top 10 will compete, with Ashleigh Barty the only confirmed exception.
Six-time champion Serena Williams will be joined by Simona Halep, Karolina Pliskova, Sofia Kenin, Elina Svitolina, defending champion Bianca Andreescu, Kiki Bertens, Belinda Bencic and 2018 champion Naomi Osaka.
Eight more Grand Slam winners are also in the women's draw, with former Wimbledon champions Petra Kvitova and Garbine Muguruza among them.