Federer reaches 4th round

Melbourne - Roger Federer came through a tough test against big-serving giant Ivo Karlovic on Friday to reach the fourth round of the Australian Open 7-6 (8/6), 7-5, 6-3.

In a contest dominated by serve, Croatia's Karlovic let slip a golden chance to take a shock lead against the 16-time grand slam champion, squandering a set point on his own serve in the first set tie-break.

Federer made no mistake, taking his first opportunity to clinch the 53-minute opener. And he rarely looked troubled after that, breaking Karlovic once in each of sets two and three.

"Obviously I knew going in it was going to be tough," said Federer, when asked about the challenge of facing the 6ft 10ins (2.08 metres) Karlovic, who holds the record for the fastest serve in the game.

"I knew it could come down to a few here and there and obviously you need a bit of luck," he said, adding: "I definitely got a bit fortunate and I started to play better as the match went on."

Serve continued to dominate in the second set but Federer seized his opportunity to break Karlovic in the 12th game, when the Croat went long with a forehand on Federer's second set point.

It was a similar story in the third set as Federer broke for the second time in the match to set up a fourth-round clash with either Bernard Tomic of Australia or Alexandr Dolgopolov of the Ukraine.

Federer, 30, who came into the clash with a 9-1 head-to-head record against his 57th-ranked opponent, is bidding to become only the second man to win five Australian Open singles titles, after Roy Emerson.

Karlovic's record serve, at a Davis Cup tie in 2011, was measured at 251 kilometres per hour (156 miles per hour).

Third seed Federer finished 2011 on a 17-match winning streak after winning titles in Basel, Paris and the ATP World Tour Finals.