Ana Ivanovic of Serbia celebrates during her victory over Marion Bartoli of France in their quarter-final match at the Indian Wells WTA tennis tournament in Indian Wells, California, March 15, 2012. [Photo/Agencies]

INDIAN WELLS, California - Former champions Ana Ivanovic and Maria Sharapova advanced to the semi-finals of the Indian Wells WTA tournament in sharply contrasting fashion on Thursday.

Serb Ivanovic completed a 6-3 6-4 upset over ailing seventh seed Marion Bartoli of France while Sharapova battled back from a set and break down to beat fellow Russian Maria Kirilenko 3-6 7-5 6-2 after a wildly fluctuating encounter.

Fifteenth-seeded Ivanovic, the 2008 champion, and second seed Sharapova, who triumphed here in 2006, will meet in the last four at the Indian Wells Tennis Garden on Friday.

Maria Sharapova of Russia celebrates winning a game against compatriot Maria Kirilenko during their quarter-final match at the Indian Wells WTA tennis tournament in Indian Wells, California, March 15, 2012. [Photo/Agencies]

World number one Victoria Azarenka of Belarus will face 18th-seeded German Angelique Kerber in the other semi-final, both having played their quarter-finals on Wednesday.

In dazzling desert sunshine, Ivanovic broke Bartoli, last year's runner-up, three times before wrapping up her quarter-final win in one hour 17 minutes when her opponent pushed a forehand service return wide.

The elegant Serb, who had ousted defending champion Caroline Wozniacki in the previous round, seized control with her powerful serving and strong baseline game after being broken in the first game of the match.

"I'm definitely very happy to be through and get my revenge for last year in the quarters," Ivanovic, who was beaten by Bartoli in straight sets at the same stage 12 months ago, said.

"I really knew I had to be aggressive. She does strike the ball a lot harder than maybe it looks."

Ivanovic, who repeatedly clenched her left fist to celebrate points won, felt her service break in the eighth game of the first set had paved the way for her win.

"That was kind of a turning point because after that we both played really solid," said the 24-year-old Serb, who became world number one for the first time after claiming her maiden grand slam singles crown at the 2008 French Open.

"That game I really stepped up another notch, I really stayed low and I was aggressive with my feet."