A "super-focused" Serena Williams joined sister Venus in the fourth round of the Australian Open Saturday, ruthlessly snuffing out Nicole Gibbs's challenge as she accelerates towards a record 23rd Grand Slam title.

The second seed clinically dispatched her fellow American 6-1, 6-3 on Rod Laver Arena, further dispelling any lingering doubts about her early-season form.

It is the 14th time in her 17 Australian Opens she has made at least the fourth round, and sets her up with a clash against 16th-seeded Czech Barbora Strycova, who beat French 21st seed Caroline Garcia.

If she gets through that, Johanna Konta, Caroline Wozniacki or Ekaterina Makarova could be waiting for her in the quarter-finals.

"It was really good to get this under my belt," she said. "I always try to take everyone super-serious and I'm always super-focused."

Williams, looking to become the most decorated Grand Slam champion in the Open era, contested just eight events in an injury-shortened 2016, concluding with the US Open.

But any doubts about her form have been put to bed in Melbourne with three comfortable wins -- including over former top-ten players Belinda Bencic and Lucie Safarova.

She hardly got out of first gear against Gibbs, dictating terms from the opening game against a player ranked 92 who had never been past the third round at any major.

Gibbs, who was only two years old when Williams made her WTA debut in 1995, was overawed and broken in the fourth game, with the 35-year-old winning every net point she contested.

It was a leisurely work-out with Williams having an answer for everything Gibbs threw at her, breaking again to race through the set in just 26 minutes.

After her second round, Williams said she had been trying to channel positive thoughts on court as she targets a seventh Australian crown, which would also take her past Steffi Graf's Open-era record of 22 major titles.

She cranked up the pressure in the second set, breaking Gibbs on a double fault to go 2-1 ahead.

Williams, who played her first match on Rod Laver Arena 19 years ago, was going through the motions but she let her guard down briefly when serving for the match, allowing Gibbs to secure her first and only break.

It only delayed the inevitable, with Gibbs promptly broken for the fifth time as Williams drew her masterclass to a close.

Melbourne Park is a happy hunting ground for Williams, who claimed her first Australian Open title way back in 2003, beating elder sister Venus in the final.

Source: AFP