Two-time Wimbledon champion Petra Kvitova says some players will not go to the US Open if current coronavirus restrictions continue.
The US Open is due to be played without fans in New York from 31 August.
The country is still reporting tens of thousands of new coronavirus cases daily and possible quarantine rules for players are unclear.
“I know a few players will definitely not go if the restrictions are like they are now,” Kvitova said.
The 30-year-old Czech 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.”
World number one Novak Djokovic has previously said he is “not sure” whether he will play, while defending men’s champion Rafael Nadal has also expressed reservations.
The US has reported more than 3.4 million cases of coronavirus, and more than 136,000 deaths nationwide, according to Johns Hopkins University.