AFP - Kim Clijsters was forced to pull out of her Brisbane International semi-final against Daniela Hantuchova with a hip injury on Friday, but remained confident of making the Australian Open.

Clijsters, the defending Australian Open champion, had taken the first set in Brisbane in a tiebreak but was down by a break of serve early in the second when she called for the trainer before taking an injury time out.

She came back on court and tried to continue but conceded the match, the Slovak winning 6-7 (4/7), 3-1 to move into the final against Estonia's Kaia Kanepi.

Kanepi progressed when she beat third seed Francesca Schiavone 6-3, 6-0, with the Italian also needing treatment after becoming ill during the second set with a stomach upset.

Clijsters said she felt the muscles in her left hip tighten during the first set and opted for caution with the first Slam of the year only nine days away.

"I couldn't go forward and I couldn't put any pressure on when I was going for my serve, it was just spasm-ing up and it was getting worse throughout the first set," she said.

"The smartest choice was to not let it get any worse."

Clijsters will have an MRI on Saturday to determine the seriousness of the injury.

Her treatment "will depend on what happens tomorrow", she said. "If the results are all clear then it's the usual -- relaxation, loosening up the hip and then gradually building up the strength in the muscles again."

Clijsters is the second high-profile casualty of the Brisbane International following Serena Williams' ankle sprain in the second round.

Hantuchova also benefited from that injury with Williams withdrawing from their quarter-final, handing the Slovak passage into the semi-finals.

Clijsters, who had an injury-plagued 2011 and played only eight tournaments throughout the year, said her style of tennis made injuries almost inevitable.

She suffered shoulder, wrist and ankle problems in the early part of the year and had not played since September after ending her season early due to an abdominal injury.

"The tennis I play is physically so demanding on the body, combine that with a hard court, it's more demanding on the joints," she said.

"I don't doubt that there will be a problem once I start in Melbourne, but that's also one of the reasons (I stopped) because I could feel it when I was serving and landing -- it was stiffening up and I didn't want it to go into a complete spasm where the muscle can actually tear.

"I hope that doesn't come out of the tests tomorrow. I don't think I've taken it that far but when you feel it getting worse and worse, you don't really have a choice."

She added: "With my stomach muscle I knew straight away that this was something that was going to take a long time (to heal).

"With this one I kind of have an okay feeling. If everything comes out okay tomorrow then it should take little under a week to get completely healed and that's what I'm hoping for and aiming for."

Hantuchova said she only noticed there was a problem when Clijsters called for the trainer.

"Kim is the kind of a player that she wouldn't ask for the trainer if there was no reason, but I was just focusing on my game so much that I didn't notice until she came over to the net (to shake hands)," she said.