BREE, Belgium - Kim Clijsters' comeback to the WTA Tour will be postponed due to a knee injury, the former World No.1 announced on social media today.

"I've had to make the decision that I will not be able to compete in January," wrote the 36-year-old. "I am undergoing rehab and treatment for a knee injury. It's a setback but I'm determined as ever to get back to the game I love. I really appreciate all your support and encouragement."

In September, Clijsters announced her return to professional tennis after a seven-year absence, intending to begin her comeback during the 2020 Australian swing. The mother-of-three turned pro in 1997 and first retired in 2007, returning two years later after having oldest daughter Jada for a glittering second career in which she won three Grand Slams, taking her overall total to four.