Australian Open champion Victoria Azarenka reached her second straight Wimbledon semifinal, while a battle of the last two champions saw four-time titlist Serena Williams take down defending champ Petra Kvitova on Tuesday at The Championships.

The second-seeded former world No. 1 Azarenka got past game Austrian Tamira Paszek 6-3, 7-6 (7-4), while the sixth-seeded Williams doused the No. 4 seed Kvitova in 6-3, 7-5 fashion under the roof on Centre Court at the All England Lawn Tennis Club. Rain forced officials to close the $80-million translucent roof on Day 8.

Azarenka and Williams will square off in a marquee semifinal here on Thursday.

The 22-year-old Azarenka looked sharp in the opening stanza against Paszek, who was appearing in her second straight Wimbledon quarterfinal, en route to an easy set win.

But Paszek would test the Belarusian slugger in the second.

Azarenka broke Paszek at love to grab a 5-4 lead in the second set, but the Austrian broke right back to even things up.

The Belarusian star broke again for a 6-5 edge, but Paszek, again, broke right back to send the second set into a tiebreak.

In the extra session, Paszek saved a first match point with a big backhand winner to pull within 4-6, but the Belarusian converted on her next match point when Paszek sent one final backhand long after 1 hour, 49 minutes of indoor tennis.

Azarenka popped seven aces and broke Paszek three times, compared to only one break for the hard-luck loser.

The Belarusian standout will now appear in her third major semifinal (1-1).

Williams, meanwhile, bounced the big Czech Kvitova in 84 minutes behind by some brilliant serving. The former world No. 1 star hammered 13 aces, avoided any double faults, and allowed only one break-point chance, which Kvitova was unable to convert on Day 8. Williams smacked three aces in the final game to seal the deal.

A determined Williams won the first set easily and got the key break she needed in the second to grab a 6-5 lead when the lefthanded Kvitova netted an errant forehand. In the next game, Williams converted on her first match point by unleashing an unreturnable serve.

Williams bested Kvitova in a semifinal here at Wimbledon two years ago.

A pleased Williams, who was forced to escape a pair of tough three-set matches in her previous two outings, was asked if she stepped up her game Tuesday.

"Yeah, I had to today playing the defending champ," she said after the big win. "I'm going to have to [step it up again] if I'm going to win the title. There's a lot of people vying for it still."

The 30-year-old Williams owns 13 majors titles, including four in this London suburb, where she's also a two-time runner-up. The powerful American will appear in her eighth Wimbledon semifinal (6-1).

Williams will meet Azarenka for a ninth time, with the American comfortably leading their lifetime series, 7-1. Williams beat Azarenka in a Wimbledon quarterfinal in 2009 and topped her on some blue clay in Madrid earlier this season.

In a match that started on Court 1 but finished on Centre, third-seeded Pole Agnieszka Radwanska held off 17th-seeded Russian Maria Kirilenko 7-5, 4-6, 7-5. The two women started the day on Court 1, but because of rain delays throughout the day, they were forced indoors to finish off their quarter, which ended almost eight hours after it started.

Radwanska converted on her first match point against Kirilenko when the Russian misfired wide on forehand after 2 hours, 50 minutes of court time.

The Polish Radwanska tallied one more break (6-5) than Kirilenko, who fired nine aces in a losing effort.

Radwanska, who owns three WTA titles this year, will now appear in her first- ever Grand Slam semifinal. She had been 0-5 in her previous major quarterfinals.

The 23-year-old, who has a shot at claiming the No. 1 ranking this week, will meet eighth-seeded German Angelique Kerber in the final four.

Kerber outlasted her 15th-seeded compatriot Sabine Lisicki 6-3, 6-7 (7-9), 7-5, also on Centre Court.

The lefthanded Kerber needed five match points to finally put away Lisicki, who ousted world No. 1 Maria Sharapova here on Monday.

The 2011 Wimbledon semifinalist Lisicki saved three match points in the second set, including a second one when she safely landed an easy forehand volley to cap a super rally between the two women in the 10th game of the stanza. Lisicki went on to win that game and level the set at 5-all.

Kerber lost a third match point when Lisicki ripped a backhand winner to even the second-set tiebreak at 7-7.

In the deciding see-saw third set, Lisicki broke for what appeared to be a safe 5-3 lead, as Kerber sulked around the court for most of the stanza. But Kerber broke right back, then held, broke Lisicki again for a surprising 6-5 advantage, and closed out the match with an easy hold. Lisicki saved a fourth match point with a forehand winner down 5-6 in the third, but Kerber finally connected on a fifth match point when Lisicki sent one final backhand wide on tennis' most-famous court.

Kerber prevailed in 2 1/2 hours despite a 10-ace effort from the big-serving Lisicki. Kerber, however, broke Lisicki eight times, while the Day-8 loser settled for five breaks of serve. Lisicki struck 38 more winners (57-19), but also piled up 37 more unforced errors (50-13).

The 24-year-old Kerber improved to 16-1 in three-set matches this season, with her only loss coming in a grass-court final in Eastbourne two weeks ago.

Kerber will appear in her first Wimbledon and second career Grand Slam semifinal. She reached the semis at last year's U.S. Open.