The world number three's absence means she is unable to defend the crown she won in 2010.
"Unfortunately I will not be able to defend my US Open title this year because of a stomach muscle injury. Two weeks of rehab was not enough to heal this injury," said the Belgian.
"Obviously I'm very disappointed. I trained very hard this summer and felt in a good shape to play the US Open."
Injury has forced the 28-year-old to miss the French Open and Wimbledon already this year.