Debutant World No.3 Maria Sharapova defeated another debutant Belgian Kim Clijsters 6-2, 7-5 for a spot in the semi-finals at the London Olympics.

"I knew I had to step it up today and stay extra focused," said Sharapova. "Kim is such a tough competitor. Obviously she has won so many Grand Slams. She has endless experience.

She added " We've always had difficult matches, and I was really happy I was able to step it up today, compared to my previous matches here. An opponent like Kim can obviously turn the match around at any time."

Clijsters later said "Of all the matches I've played against her in my career, this is the best she has ever served. On grass it's going to be tough to beat her.

"It was great. It's a nice experience every time you go out on Centre Court. I'm so happy to say my last match at Wimbledon was on Centre Court."

Sharapova will next face countrywoman Maria Kirilenko, who stunned sixth seeded Petra Kvitova 7-6(3), 6-3. 

An all-Russian semifinal at the Olympics means one will win gold or silver, and the other could win the bronze.