No. 10 Naomi Osaka did not initially enter but has asked for a wild card, her management team confirmed Thursday.
The Western & Southern Open, which has a long history as the most significant tune-up for the US Open, was moved to New York from its long-time home in Cincinnati due to the coronavirus pandemic. It will immediately precede the US Open starting Aug. 20 in a "safety bubble" at the National Tennis Center.
Seven of the top eight men are on the acceptance list for the Western & Southern, with only inactive Roger Federer missing.
The women's field will feature three former champions: Williams, Garbine Muguruza and Karolina Pliskova. Also entered are No. 8 Belinda Bencic, two-time Wimbledon champion Petra Kvitova, and rising stars Coco Gauff and Amanda Anisimova. No. 17 Elena Rybakina, who led the tour in 2020 with 21 wins in the months preceding the mid-March halt of the tours, is also entered.
Williams has been one of the most enthusiastic supporters of the USTA's plan despite the strict health protocols, including the prohibition of spectators, that will govern the event.
Rapidly closing on age 39, Williams has an Open-era record 23 Grand Slam singles titles -- one short of the all-time record held by Margaret Court.
Williams is launching her return to tour tennis along with a number of other stars, including sister Venus Williams, Sloane Stephens, Victoria Azarenka and Gauff at the Top Seed Open on Aug. 10 in Lexington, Kentucky.
Barty and Halep have long expressed reservations about playing in the US Open. Barty, Osaka and Andreescu have not taken part in any of the exhibition events of the past few months and their participation for the rest of 2020 is in question.
Halep had planned to return at the Palermo Ladies Open, but due to concerns about travel restrictions, she will play at the Prague Open, also starting Aug. 10.