Petra Kvitova says there is no guarantee she will compete in the US Open and she knows of players who will definitely not enter the draw in the current climate.
Flushing Meadows is set to stage what will be the second major of the year behind closed doors from August 31 to September 13.
Over 32,000 people in New York state have died after contracting the coronavirus, with more than 431,000 cases reported.
US Open organisers vowed that the tournament will go ahead in the "safest manner possible, mitigating all potential risks".
Two-time Wimbledon champion Kvitova says some players will not travel as it stands.
"I know a few players will definitely not go if the restrictions are like they are now," the world number 12 from the Czech Republic told BBC Radio 5 Live.
She added: "I'm still thinking of what everything will look like, what the restrictions will be, how many people we can take and if they quarantine us."
Kvitova, who has been playing in front of fans at a grass-court exhibition tournament in Berlin this week, is not 100 per cent sure she will head out to the United States next month.
She said: "Playing without the fans in grand slams, I can't really see it.
"If that happens and everything is okay, I will go for sure to compete but there's still a chance I will not go. I will decide when I know everything."
The WTA Tour is set to resume at the Palermo Ladies Open on August 3.