NEW YORK (AP) — Two-time Australian Open champion Victoria Azarenka withdrew from the U.S. Open on Monday because she was unable to resolve a custody dispute with her infant son's father.

The 28-year-old star from Belarus gave birth to her first child in December and she returned to the tour in June. She detailed the dispute with the boy's father in a long Twitter post last week, saying she might not be able to bring her son with her to New York.

"I am sadly unable to compete in this year's U.S. Open due to my ongoing family situation that I am working through," Azarenka said in a statement.

In last week's post, Azarenka wrote that she separated from Leo's father shortly after Wimbledon, where she lost to Simona Halep in the fourth round on July 10.

"As we work to resolve some of the legal processes, the way things stand now is that the only way I can play in the U.S. Open this year is if I leave Leo behind in California," Azarenka wrote, "which I'm not willing to do."

Azarenka has not played since Wimbledon, and the former No. 1 player is now ranked 204th. She was the runner-up in New York in 2012 and 2013, losing in the final each year to Serena Williams. Those were also the years that Azarenka won her two Grand Slam singles titles in Australia.

Williams, who is pregnant with her first child, also will not play in this year's U.S. Open. On the men's side, three top-10 players have withdrawn with season-ending injuries: defending champion Stan Wawrinka, Novak Djokovic and Kei Nishikori.

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