WIMBLEDON, England — After eight days of nearly uninterrupted tennis, rain disrupted the men's quarterfinals at Wimbledon on Wednesday and slowed five-time champion Roger Federer's bid to extend his grass-court winning streak to 64 matches.

After the start of play was held up by nearly an hour, Federer raced to a 6-1, 1-1 lead over Mario Ancic before the rain came again and the covers were rolled back onto Centre Court.

On Court 1, Feliciano Lopez was leading Marat Safin 5-2 when play was suspended.

Organizers said the weather was expected to clear up later in the day.

Federer walked onto Centre Court in his custom-made cardigan just after 1:45 p.m. and glanced up at the threatening skies.

It looked like he wanted to get things over as quickly as possible against Ancic, the last man to beat him at Wimbledon — in the first round in 2002.

Federer charged through the first set in 20 minutes — winning 12 of the first 14 points, hitting six aces and winning 16 of his 17 service points.

This was Federer at his vintage best, gliding across the court and ripping shots that flew past Ancic or forced him into errors. The two held serve to open the second set before the rain came again.

Since losing to Ancic six years ago, Federer has won 63 consecutive matches on grass and 38 in a row at the All England Club. He's also won five straight against Ancic.

Other than a 1 hour, 41 minute rain delay at the start of play last Friday, Wimbledon had basked in remarkably good weather until now.

Rafael Nadal, bidding to become the first man to win the French Open and Wimbledon in the same year since Bjorn Borg in 1980, was due to play Andy Murray in the second quarterfinal on Centre Court. The 12th-seeded Murray, playing in his first Grand Slam quarterfinal, is trying to become the first British man to win the title in 72 years.

The winner of that match will advance to the semifinals against No. 94-ranked Rainer Schuettler or No. 145-ranked Arnaud Clement. The 32-year-old Schuettler will be playing in his first Grand Slam quarterfinal in five years, and Clement last reached the final eight at a major in 2001.

Two-time major champion Safin was playing in his first Grand Slam quarterfinal since winning the Australian Open in 2005.

The women's tournament, meanwhile, seems headed toward the first all-Williams final in five years.

Venus and Serena Williams, who between them have won six of the last eight Wimbledon titles, are one round away from a third Wimbledon title matchup and seventh Grand Slam championship showdown. Neither has dropped a set so far, and their power games have set them apart from the rest of the women's field.

Next up for two-time champion Serena in Thursday's semifinals is Zheng Jie, who became the first Chinese player to reach the semifinals of a Grand Slam by beating Nicole Vaidisova 6-2, 5-7, 6-1. The 133rd-ranked Zheng is also the first wild-card entrant to reach the women's semis at Wimbledon and second at any Grand Slam.

Defending champion and four-time winner Venus will next face No. 5 Elena Dementieva, who wasted a 5-1 lead and two match points in the second set before beating fellow Russian Nadia Petrova 6-1, 6-7 (6), 6-3 to reach her first Wimbledon semifinal.

Don't tell Serena that Venus is the one to beat at Wimbledon.

"I would never sit here and say she's the favorite when I'm still in the draw," she said, bristling at the suggestion. "That's not me. I always believe that I'm the favorite. Even if I'm not the favorite, I'm always going to believe that I am."