The US Tennis Association is planning to stage the two tournaments back-to-back in NY while the coronavirus outbreak worsens in other parts of the country and there are lingering questions about worldwide travel.
"My team and I have decided that we won't be traveling to the U.S. and Western and Southern Open and the U.S. Open this year", Barty said in a statement issued by her manager on Thursday.
Less than four weeks for the foreseeable return of the ATP circuit (the WTA will do it next Monday in Palermo, Italy), The Cincinnati combined tournament (August 22-28), to be played in the NY "bubble", published its "entry list", the list of registered participants.
Barty has joined world No. 2 Simona Halep of Romania, No. 6 Bianca Andreescu of Canada and No. 10 Naomi Osaka of Japan for not playing in the U.S. Open.
The Western and Southern Open is scheduled for August 20-28 on the same hard courts at the Billie Jean King National Tennis Center that are slated to host the US Open from August 31 to September 13.
Williams, in search of her 24th career Grand Slam singles title, already said she will play in the U.S. Open.
Former men's champions who have entered the ATP Masters 1000 event also include the top two players in the ATP Rankings - world number one Djokovic (2018 winner) and world number two Nadal (2011) - along with Grigor Dimitrov (2017) and Marin Cilic (2016).