MELBOURNE - Roger Federer cut Croatian power-serving giant Ivo Karlovic down to size to join grand slam rival Rafael Nadal in the fourth round at the Australian Open on Friday.

The Swiss all-time slam champion, confronted with the tallest challenge in men's tennis, had all the answers in a composed 7-6 (8/6), 7-5, 6-3 win over the towering 2.08m Karlovic in 2 hours, 17 minutes.

Federer, bidding for a fifth Australian title, now takes on the winner of the battle between Alexandr Dolgopolov and Bernard Tomic in the round of 16.

The world No 3 remained on track for a semifinal with Nadal, who reeled off his third straight-sets victory in the tournament in accounting for Slovakian qualifier Lukas Lacko.

Federer improved to 10-1 in matches against Karlovic, swinging the match with a tense opening set tiebreak win and breaking the 57th-ranked Croat's serve twice, while conceding only two break points in 17 service games.

In a contest dominated by serve, Karlovic let slip a golden chance to take the lead, 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.

"Obviously I knew going in it was going to be tough," Federer said.

"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."

The Swiss hit 24 forehands among his 55 winners and only made 13 unforced errors in 33 games.

Spanish world No 2 Nadal, bidding for his 11th grand slam title in Melbourne, wore down Lacko after a fiercely contested opening to claim a 6-2, 6-4, 6-2 victory.

Nadal has yet to drop a set in his three wins at the year's opening major tournament and will face compatriot Feliciano Lopez in the round of 16 on Sunday.

Lopez, the 18th seed, needed almost three and a half hours to get on top of 16th-seeded Isner, 6-3, 6-7 (3/7), 6-4, 6-7 (0/7), 6-1.

Nadal has only failed once to reach the fourth round in eight visits to Melbourne, but he denied it was all coming too easily this year.

"I did well. I played three matches at very good level. Today was one of the best, solid, without mistakes, comfortable with the serve and good returns," Nadal said.

"Nothing is easy. Everything is difficult. Every match you have your problems. First set was 6-2, but I had to fight for it. It was a tough one."

"But I played solid all the match, so that's why I won."

Nadal wore down the 119th-ranked Lacko after being forced to work hard at the start of the match. The opening point was a 28-shot rally and the first two games occupied 14 minutes with the Spaniard losing his opening service game.

But the second seed went on to break Lacko's serve six times to complete victory in 1hr, 55min on Rod Laver Arena.

Nadal is currently joint sixth with Bill Tilden on the list of all-time grand slam men's singles champions behind Federer (16).

Agence France-Presse