Kim Clijsters has withdrawn from the Western & Southern Open because of an abdominal injury.
The 37-year-old, who has won three of her four grand slam titles at the US Open, came out of retirement last September and lost to Garbine Muguruza on her return to the WTA Tour in Dubai six months ago.
She suffered defeat to Johanna Konta in Monterrey but the coronavirus-enforced suspension of the season put her comeback on hold.
The Belgian's injury restricted her involvement in the 2020 World Team Tennis season, in which her New York Empire team emerged triumphant this month.
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And she will not take part in an event moved from Cincinnati to the Flushing Meadows bubble put in place for the US Open.
Clijsters, who will remain in the bubble for what is now the second of only three slams in 2020, said in a statement: "I'm grateful to the Western & Southern Open for the opportunity to play the tournament once again.
"I have great memories of playing in Cincinnati and was looking forward to being a part of the event this year.
"It's disappointing to have to withdraw but I need a little more recovery time.
"I'm grateful to be able to stay in the "bubble" and continue to prepare with my team here at the USTA Billie Jean King National Tennis Center.
"I want to thank the Western & Southern Open team, the USTA and WTA for all their efforts in putting these events together - they've worked really hard to create a great experience in a safe and healthy space for players."
The US Open gets under way behind closed doors on August 31.