US Open 2011: Serena Williams & Caroline Wozniacki reach last 32

Williams is the tournament favourite despite being seeded 28th

Serena Williams gave another ruthless display as she thrashed Michaella Krajicek to reach the third round of the US Open in New York.

The American powered past her Dutch opponent 6-0 6-1 and has lost just three games in her opening two matches.

Williams is seeded 28th after a lengthy absence through injury and will face fourth seed Victoria Azarenka next.

World number one Caroline Wozniacki of Denmark hammered Arantxa Rus 6-2 6-0 in the night session.

"I feel like I'm on a roll and I'm playing well," said Wozniacki. "I believe I can beat anyone on a good day but I have to play on a high level for seven matches, and that's not easy."

Azarenka looked to have a tricky draw against Argentina's Gisela Dulko and was out on the Grandstand court until late in the evening before she secured a 6-4 6-3 victory, setting up a fascinating clash with Williams.

"I feel I'm definitely going in as the underdog because she's won more tournaments and she's been doing a lot," Williams said of playing the Belarusian.

"I feel like I have nothing to lose in this match if I have to play her."

Eleventh seed Jelena Jankovic saw off Australia's Jelena Dokic 6-3 6-4 despite needing treatment on her back several times during the match.

"I hurt it in the first set," said the Serbian, runner-up in 2008. "I felt a little restricted when I was hitting my serves and especially when I had to bend down when I was waiting to return her serves.

"I have a day off tomorrow and I will just try to receive some treatment and feel the best as possible for my next match. I think I will be OK."

Seventh seed Francesca Schiavone hammered Mirjana Lucic 6-1 6-1, while 10th seed Andrea Petkovic battled through 3-6 6-3 6-3 against Zheng Jie.

The German tore the meniscus in her right knee in Cincinnati last month and had not been sure she would compete in New York.

"I didn't know if I was going to play at all, so every match that I win is just a huge, huge victory for me," said Petkovic.

Ana Ivanovic, the 16th seed, made it to the last 32 without hitting a ball when Petra Cetkovska withdrew ahead of their match with an injured quadriceps.

"It's never nice to win this way," said Ivanovic. "But I'd be lying if I said I wasn't happy to be through to the next round."