In hot and blustery conditions, the Spanish world number one crushed Roko Karanusic of Croatia 6-2, 6-3, 6-2 to stay on track for his first hardcourt Grand Slam title.

In contrast, Williams needed to mount a second set recovery after Gisela Dulko took a 5-2 lead. The American finally woke up to reel off five games in a row and tame the Argentinean 6-3, 7-5.

Nadal wrapped his one-sided match in 97 minutes to set up a clash with 79th-ranked German Tommy Haas. "He played aggressively, it's not easy to play against someone who plays inside the court and hits big shots with the forehand," Nadal said. "But I feel very comfortable here and I'm very happy with the victory."

Williams acknowledged her performance had not been good, rating it a D minus. "Today I was at like a D minus at best," she said. "But it's good that I was able to win, too, when I wasn't playing my best. I definitely will try to do better. She had some opportunities but I never felt like I was going to lose."

She joins top seed Jelena Jankovic, third seed Dinara Safina and fifth seed Ana Ivanovic in the third round after they all assured their berths on Wednesday. Sister Venus plays later on Thursday.

While the Williams' are considered favourites, the unassuming Elena Dementieva is in a rich vein of form. The Russian fourth seed steamrolled over Czech Republic's Iveta Benesova, 6-4, 6-1 for her 12th straight victory this year after claiming back-to-back titles in Auckland and Sydney.

The Beijing Olympic gold medalist is seen as one of the most consistent players never to have won a Grand Slam and she senses her time is coming.

"I'm not thinking about my chances," she insisted. "I'm really enjoying the way I'm playing right now and I just want to go as far as I can, just enjoy every single match I play here."

Also safely through was eighth seed Svetlana Kuznetzova and 2006 champion Amelie Mauresmo, who survived a scare from British qualifier Elena Baltacha to win 4-6, 6-3, 6-2. The experienced Frenchwoman, in her 14th year of Grand Slam tennis, warned she would get better as the tournament progressed.

"I've been playing a lot of Grand Slams now, and I know that you cannot really define your game from what you can see in the first couple of rounds," she said. "But I'm expecting to play better and better as the tournament goes on."

Next up for her is dark horse Victoria Azarenka, who continued her recent impressive form by breezing past the Czech Republic's Petra Kvitova 6-2, 6-1.

The Belarusian teenager, ranked 14 in the world, lurks as an outside chance here after winning her first WTA tournament in Brisbane two weeks ago.

Among the men, Chilean 13th seed Fernando Gonzalez sped past Argentina's Guillermo Canas. The 2007 finalist out-punched Canas in a tight first set before winning 7-5, 6-3, 6-4 in two hours and 19 minutes, setting up a clash with 24th seed Richard Gasquet.