World No 1 Roger Federer booked his place in the Australian Open semifinals with an unconvinving win over Tommy Robredo. He will face big-serving US ace Andy Roddick, who smashed passed former flatmate Mardy Fish in straight sets.

In the women's draw, seven-time Grand Slam champion Serena Williams, who won here in 2003 and 2005, staged an amazing fightback to down Israeli 16th seed Shahar Peer 3-6, 6-2, 8-6 in an epic battle and will meet Czech teenager Nicole Vaidisova in the semis.

Federer made a series of uncharacteristic errors in his quarterfinal with seventh seed Tommy Robredo of Spain, before he re-established order to win 6-3, 7-6 (7/2), 7-5.

"It was a tough straight sets win," said the Swiss world number one, who was playing in front of his parents and sisters, who jetted in from Europe.

"I had to work really hard tonight. It was breezy so we had to adjust."

Federer established a new Open-Era record of 11 consecutive Grand Slam semifinal appearances in beating Robredo, overtaking Ivan Lendl.

He has yet to drop a set and has a 12-1 record against Roddick, but he knows the American is playing well.

"I'm really looking forward to playing Andy. He's in good form so I'll need to be at my best."

It was a simpler exercise for Roddick against the unseeded Mardy Fish, wrapping up a 6-2, 6-2, 6-2 win in one hour 27 minutes, just four minutes longer than it took Williams to get through her third set.

Williams rallied from a set down to lead 4-1 in the final set before her gritty opponent, the first Israeli woman to reach a Grand Slam quarterfinal, pulled level.

But Williams drew on all her experience to carry her through.

"I feel awesome. I'm the ultimate competitor," said the elated Williams, who came into the tournament unseeded after an injury-hit 2006.

"It's exciting to come through. I'm just happy to be out there and competing. I feel absolutely no pressure. Definitely ready to create some more carnage, hopefully."

Tenth seed Vaidisova won an all-Czech quarterfinal 6-1, 6-4 against unseeded Lucie Safarova, who dumped defending champion Amelie Mauresmo out of the tournament.

The 17-year-old, who made the French Open semis last year, belied her tender years with a ruthless performance and broke her opponent twice early in the match then served out the first set with an ace.

The lanky world number 12 maintained the pressure and put her big-match experience to good use to end Safarova's challenge after one hour 11 minutes.

"Definitely very, very happy and excited," said Vaidisova, who is the youngest player left in the tournament.

"The first Grand Slam of the year, you have some off season. You don't know how you're going to come back. But I had a great start to the year and I just keep improving," she said.

With Safarova out the way, she is already looking forward to meeting Williams on Thursday.

"I've never played Serena before. She's definitely a great champion. I expect a tough match from her," she said.

Roddick was in a class of his own in a mis-match against his former room-mate Fish in an all-American clash.

The sixth seed made just four errors in the entire match as Fish self-destructed with a flurry of volleying errors.

"I've made that many errors in the first game of a match before so I thought I played pretty well today and I'm excited to be through to the semis," Roddick said.

(China Daily via AFP January 24, 2007)