Clijsters may not be able to defend US Open title

Kim Clijsters' US Open title defence is in doubt after she pulled out of the WTA Toronto hardcourt tournament on Tuesday with a stomach muscle injury.

Clijsters was leading 6-3, 1-2 in her second-round match against China's Zheng Jie when she hit a forehand, shook her head and departed. It was another setback for the Australian Open champion from Belgium, who injured her right ankle in April and then pulled out of tournaments in Rome and Madrid with right shoulder and wrist injuries.

Clijsters said she still hoped to defend her title at the US Open, the final Grand Slam of the season that starts on August 29 in New York. "I still have a few weeks till (the US Open) and we'll try to do everything to be ready. During the match it just felt like it went worse," said Clijsters, who delivered an unusual six double faults before calling it a day after 54 minutes on court.