World No.1 Roger Federer survived a fright against German Tommy Haas before winning his fourth-round Australian Open match in five sets.

Federer won 6-4 6-0 3-6 4-6 6-2 to advance into the quarter-finals.

It was the first time he had conceded a set in the tournament.

He will next play Russian Nikolay Davydenko in the quarter-finals.

Federer said he had remained confident of getting over the line against Haas.

"I wouldn't call it an escape tonight. I thought I was pretty much in control of the match," Federer said.

"I haven't had too many five-setters in the last couple of years. It's a different atmosphere.

"It's not something I'm really used to. This is maybe why I'm so happy."

Haas said he was proud of his performance and Federer had simply been too good in the final set.

"Everybody that's up against him is saying I've got to play my best and hope for his not-so-good day and try to push him," he said.

"I think I pushed him as much as I could tonight.

"At 2-2 you saw why he is the best. You've just got to tip your hat and say unbelievable."

Federer plays Russian Nikolay Davydenko in the quarter-finals, against whom he has a 6-0 head-to-head record.

Federer is the only one of the eight men in the quarter-finals to have won a grand slam tournament.

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