Former world No.1 Roger Federer has overcome a stern challenge from American qualifier Noah Rubin to advance to the third round of the Australian Open in straight sets.

The 20-year-old New Yorker made the four-time Melbourne Park champion work harder than Wednesday's 7-5 6-3 7-6 (7-3) scoreline suggested.

"He's a great fighter ... he's aggressive on the ball and I think he had the upper hand on the baseline," Federer told the Seven Network.

"I think my serving kept me in the match today ... I'm happy I got through somehow.


"I wasn't feeling as good (late) as in the beginning. I definitely got a little lucky in that third set ... so it was good to fight through."

Federer saved two set points in the third after Rubin - ranked 200th in the world - broke him in his opening service game.

The 17-time grand slam winner broke back in the ninth game of the set to take it to a tiebreaker and converted the first of three match points after a Rubin double fault.

Federer will play 10th seed Tomas Berdych in the third round after the Czech's straight-sets defeat of American Ryan Harrison.