BEIJING — Even by the lofty standards of the Williams sisters, three victories at the Olympics is a good day's work.

They won in singles and doubles Tuesday, and the toughest match was the one they played together. Venus and Serena rallied in first-round doubles to beat Iveta Benesova and Nicole Vaidisova of the Czech Republic 4-6, 7-5, 6-1.

Earlier, the Williamses won second-round singles matches. Serena beat Samantha Stosur of Australia 6-2, 6-0, and Venus swept Benesova 6-1, 6-4.

The sisters could meet in Saturday's singles final.

"That would be fantastic," Venus said. "Obviously, it's a long ways away, but the third round makes it closer. I'm really excited for both of us to be playing really well for the U.S."

In men's singles, No. 1-seeded Roger Federer and No. 2 Rafael Nadal moved one round closer to renewing their rivalry in Sunday's final.

Federer beat Rafael Arevalo of El Salvador 6-2, 6-4. Rafael Nadal sustained his summer surge by defeating Australian Lleyton Hewitt 6-1, 6-2.

"Very happy about my performance," Nadal said. "I think I play one of my best matches in the last weeks on hard court."

This year's French Open and Wimbledon champion, Nadal is assured of climbing to No. 1 in the rankings next week, ending Federer's 4½-year reign.

Nadal and Federer seek their first Olympic medal, while the Williamses are trying to add to the family collection. They won the gold in doubles at Sydney in 2000, and Venus won the singles that year.

"I've never played singles at the Olympics, so this has been really cool for me," Serena said. "Every time I walk out there, it's like I'm playing in my match, but at the same time I have the whole U.S. team on my side. It's good. I really like that feeling."

Teammates Lindsay Davenport and Liezel Huber won their first-round doubles match, beating Klaudia Jans and Alicja Rosolska of Poland 6-2, 6-1. Davenport said a knee injury that forced her to withdraw from singles last week didn't bother her in the match.

"It has slowly been feeling better," she said. "It's hard to train for singles and always dealing with swelling. I've just really been playing careful with it. I really wanted to be here in whatever capacity it was, and it became painfully obvious to me that role was doubles. I was very happy to accept that and move forward."

No. 1-seeded Mike and Bob Bryan of the United States won their opening match in doubles, defeating Mark Knowles and Devin Mullings of the Bahamas 6-2, 6-1.

In women's singles, new No. 1 Jelena Jankovic beat Alona Bondarenko 7-5, 6-1. Jankovic supplanted Ana Ivanovic atop the rankings Monday.

On the men's side, No. 3 Novak Djokovic beat Rainer Schuettler 6-4, 6-2.

With the temperature rising and the sun making its first appearance at the Beijing Games, the stands became a sea of fluttering Chinese fans — the hand-held kind — for Serena Williams' morning match on cozy Court 1.

"It was early," she said. "But with the time difference, I'm still waking up, like, at 5 in the morning. So it's good. I like the early matches."

She was done in 44 minutes. From 2-2, Williams won 40 of the final 49 points and 10 consecutive games. She whacked service winners, overpowered Stosur from both wings on the baseline and came forward for an overhead slam that prompted an appreciative "Ooooh" from the crowd.

Williams punctuated her best shots with a fist pump. She made the gesture one last time after ripping a backhand return winner on match point, then shouted "Come on!" as she trotted toward the net and into the round of 16.

Williams lost just five points in the second set, and dropped only six points on her serve in the match.

"My way of improving on it is to keep it up," said Williams, who is seeded fourth. "I played really clean matches in the past, the next one would be kind of streaky. I don't want to do that any more. I just want to keep playing the same consistency."

No. 7-seeded Venus Williams was less dominating because she struggled with her forehand and second serve, hitting six double-faults. But she never faced a break point and lost only two of 24 points on her first serve.

"I felt like any time that I needed to serve well, I did — if I was down love-30, or a 30-all point," she said. "That's good for me going on in the later rounds, that I'm tough on my serve."