MOSCOW (AP)—Top-ranked Jelena Jankovic defeated Flavia Pennetta 7-6 (6), 6-3 Friday to advance to the semifinals of the Kremlin Cup.

“It was a tough match for me today and I didn’t play the way I wanted to,” Jankovic said. “I felt a bit tired and was struggling.”

The 23-year-old Serb will face defending champion Elena Dementieva, who beat Nadia Petrova 6-4, 4-6, 7-6 (6).

“She is the strongest player in the world,” Dementieva said of Jankovic. “She’s playing terrific tennis and has just won back-to-back titles on different surfaces. It won’t be an easy match.”

Jankovic took the top ranking from Serena Williams on Monday after winning back-to-back titles at the China Open and Porsche Grand Prix in Stuttgart, Germany. Jankovic will retain her top ranking next week regardless of the results in Moscow because Williams, the runner-up in Moscow last year, pulled out because of injury.

After trading serves two times in the first set, Jankovic broke Pennetta for a 6-5 lead but the Italian broke back to force a tiebreaker. Pennetta was 3-0 up, then 5-3 down, but evened it 6-6 before returning wide on the next two points.

The 18th-ranked Italian, 3-2 up after breaking Jankovic in the opening game of the second set, saved five break points in the sixth game before Jankovic finally broken her on the 12th deuce to even it 3-3. The Serb won three more consecutive games to close the match.

Petrova went 4-3 up in the all-Russian match with a break in the seventh game of the first set, but Dementieva won three consecutive games to take the set. Dementieva was leading 4-1 in the second set but Petrova came back strongly and won five consecutive games to level the match at one set each.

In the third, Dementieva again took a 4-1 lead but Petrova rallied back to 4-4 and both players held their serves to force a tiebreaker. Dementieva won on her third match point.

“It was not an easy match,” Dementieva said. “There were many missed chances for me .”

Vera Zvonareva also advanced, defeating Dominika Cibulkova 7-5, 6-4.

In men’s quarterfinals, veteran Fabrice Santoro won the first set 6-3 and was 2-0 up in the second when his fellow Frenchman Paul-Henri Mathieu, seeded fourth, retired because of illness.

Santoro, who will turn 36 in December, won his only title this season in Newport in July.

Mischa Zverev rallied from 5-1 down in the third set to advance to his first career ATP Tour semifinal with a 6-4, 3-6, 7-5 victory over Viktor Troicki.

LONDON, June 19 (Reuters) – Jelena Jankovic’s books are starting to gather dust while she concentrates on a tennis career she almost gave up on and puts her studies on hold.

The Serbian is in her second year of a business degree but has found little time to study now that she has reached number three in the world and has her sights set on next week’s Wimbledon.

"Nowadays I’m a little bit behind because I’ve been doing very well on the court and I’ve been very concentrated on my tennis," the 22-year-old told Reuters in an interview.

"I will try to study little by little — my ambition is to finish."

She came close to quitting the sport last year but since then has shot up the rankings after a run of good results.

Jankovic reached the semi-finals of Roland Garros earlier this month and then tuned up for Wimbledon by defeating Maria Sharapova in the final of the Birmingham Classic on Sunday, capturing her fourth title of 2007.

Her bid to reach a grand slam final has twice been thwarted by world number one Justine Henin and so Jankovic is hoping to avoid playing the Belgian in southwest London.

"I think I have the best chance on grass against her so maybe I can be on the other side (of the draw) and meet her in the final," she said

"I love playing on grass. I feel confident on this surface so hopefully I can play the best game and do well."

ATTITUDE CHANGE

Jankovic said her rise up the Sony Ericsson WTA rankings had come after she started working hard on the physical side of her game and also altered her mental approach.

"I’ve changed my attitude and I look at things in a positive way," she said.

"I always try to learn, I don’t try to look for excuses when I lose a match, I try to analyse my mistakes and what I can do better to keep improving and becoming a better player each time."

Jankovic was one of three Serbians to reach the semi-finals in Paris. Asked if they could repeat the feat at Wimbledon, she said: "I hope it will be like that there, we will try our best."

If she continues to perform like she has this year, it could be a while before she returns to university or embarks on the alternative career she has earmarked.

"I really love acting and that is maybe something after my tennis career that I would like to pursue."