Four-time Grand Slam champion Kim Clijsters has delayed her WTA Tour comeback because of a knee injury.

Clijsters, 36, says she will not be able to compete in January as she continues rehabilitation and treatment.

"It's a setback but I'm determined as ever to get back to the game I love," the Belgian mother of three said.

Clijsters, who first retired in 2007 to start a family, says she has been "inspired" by other mothers such as Serena Williams and Victoria Azarenka.

The former world number one returned in 2009 and won three more Grand Slams before her second retirement in 2012.

When her latest return was announced in September, Clijsters said she was targeting a return in January when the 2020 season starts but added she would remain flexible in her scheduling.

As a former world number one, Clijsters is eligible for unlimited wildcards at WTA tournaments. She will need to play three tournaments or earn 10 ranking points to re-establish a ranking.

She said not having to play a set number of tournaments a year has "made the choice a little bit easier".

Clijsters won 41 WTA titles and spent 20 weeks as world number one in her two previous spells.

Her daughter Jada was born in 2008, followed by sons Jack in 2013 and Blake in 2016.