World No.2 Kim Clijsters' Australian Open ambitions have been thrown into doubt after she withdrew from the Hopman Cup with an ankle injury.

Hopman Cup tournament director Paul McNamee said his medical staff were cautiously optimistic the Belgian would be available for the opening Grand Slam of the year in Melbourne.

She will be reassessed in the next 24 to 48 hours as to the likelihood of her participation at the Open starting January 19.

"The MRI shows bruising on the bone at the back of the ankle joint, so Kim needs a combination of rest and treatment, which includes physio and anti-inflammatories," he said.

"She does need to withdraw from the Hopman Cup.

"It will be reassessed in the next 24 to 48 hours with regards to whether she could play next week in Sydney.

"The medical advice is such that they are cautiously optimistic she will be OK for the Australian Open.

Clijsters was leading Alicia Molik 6-3 6-7 (8-6) 3-2 with the tall Australian up 30-0 on serve when the Belgian retired from the contest after hurting her left ankle.

She couldn't play the much-anticipated mixed doubles match against new finance Lleyton Hewitt to the disappointment of a record crowd at the Burswood Dome.

Hewitt feared the worst before the doctor report came in on Wednesday evening.

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