Serena steps up title defence

Serena Williams stepped up the defence of her Australian Open title today with a crushing straight sets third-round win over 32nd seed Carla Suarez Navarro.

The world number one is a four-time winner at Melbourne Park but she has never successfully defended her title.

The American is on course to change that after over-powering the Spaniard 6-0 6-3.

Williams was also joined in the last-16 by her elder sister Venus, who fended off the plucky challenge of Australia's Casey Dellacqua 6-1 7-6 (7/4).

There were also straight-set wins for seventh seed Victoria Azarenka, ninth seed Vera Zvonareva and local hopeful Sam Stosur, the 13th seed.

It was the defending champion, though, who was the most impressive and she has now dropped just nine games on her march into the fourth-round.

The 28-year-old is, however, expecting a tough challenge in the next round where she will meet Stosur, a 6-4 6-1 winner over Alberta Brianti today.

The Australian beat Williams when they last met in Los Angeles last year and with her home crowd behind her the defending champion is wary of her threat.

'She beat me the last time we played, so she has a lot of momentum,' said Serena Williams.

'A ton of momentum. She serves great. She gets a lot of big, big first serves.

'I definitely expect the crowd to root for Sam. I mean, I would.'

Stosur claimed she could cause the upset, saying: 'I guess I don't really have that much to lose. I can go out there and just really enjoy it.

'I know I've got the game that can beat her because I've done it before.'

Sixth seed Venus Williams is chasing her first Australian Open title at the age of 29 and had to withstand a late challenge from wildcard entry Dellacqua.

'I think she played really well in the second set. I had a lot of chances to go up breaks at 4-1 or 5-2 and she just hung in there and kept playing tough,' said Venus Williams, who made it a hat-trick of wins against left-handers after beating Lucie Safarova and Sybille Bammer in the earlier rounds.

'It was my third lefty in a row, which is a little unusual so hopefully I'll be able to get back into the rhythm of playing right-handers.'

Williams will get her wish after 17th seed Francesca Schiavone upset Agnieszka Radwanska, the 10th seed, 6-2 6-2.

Seventh seed Azarenka has quietly made her way through the draw, but confirmed she is a threat with a 6-0 6-2 win over unseeded 32-year-old Tathiana Garbin 6-0 6-2.

It was the third consecutive match in which the Belorussian has claimed a set to love and she will next play ninth-seeded Russian Vera Zvonareva who easily overcame Gisela Dulko 6-1 7-5.

China's Li Na was the only unseeded player to go through today as she upset 22nd seed Daniela Hantuchova 7-5 6-3 6-2.

Li will pay fourth seed Caroline Wozniacki who beat Israel's Shahar Peer (29) 6-4 6-0.