Melbourne - Holder Novak Djokovic survived a struggle with Bosnian-American Amer Delic to win a battle of the Balkans 6-2, 4-6, 6-3, 7-6 (7-4) for a place in the fourth round of the Australian Open on Friday.

Serbian Djokovic, seeded third and defending a major title for the first time, saved a pair of set points in the tenth game of the fourth which would have allowed lucky loser Delic to take the contest into a deciding fifth set.

Delic played well over his ranking of 127, hammering 16 aces in a contest stretching past the three-hour mark.

Djokovic trailed on winners, with 30 to the 46 of an inspired opponent playing in a Grand Slam third round for the first time.

Djokovic is knocking on the number two ranking held by Roger Federer, who faced a showdown in the evening at Melbourne Park against 2005 champion Marat Safin.

Djokovic has been ranked third for all but one week since July, 2007, but has been within one victory of claiming number two on three occasions (2008 Hamburg, 2008 Roland Garros and Sydney last week).

Argentine eighth seed Juan Del Potro recovered from a slow start to put out Gilles Muller of Luxembourg 6-7 (5-7), 7-5, 6-3, 7-5.

Rising Croatian Marin Cilic, Croatia crushed Spaniard David Ferrer, the 11th seed, 7-6 (7-5), 6-3, 6-4 to line up against Del Potro in the next round.

"Obviously he's playing good," said Cilic, who has recently broken into the Top 20. "He won in Auckland and is coming in good form, good shape. He's playing very well.

"He will be a tough opponent to beat."

Women's third seed Dinara Safina stayed on course for a shot next week at the number one WTA ranking, gaining a victory for the Safin family hours before her brother Marat was to face Federer.

Safina, the losing finalist at the French Open, reached the fourth round in Melbourne for the first time in her career, posting a 6-2 6-2 win over Kaia Kanepi.

Safina is one of three women chasing Jelena Jankovic in the rankings with a title next Sunday enough to assure the 22-year-old of the breakthrough top spot.

Russian Vera Zvonareva, seeded seventh, beat Italian Sara Errani 6-4, 6-1 while Russian number 10 Nadia Petrova, advanced without a fight as opponent Galina Voskoboeva quit with a back injury after losing the first set 6-1.

Safina's big brother Marat, the 2005 Melbourne champion, was hoping to repeat his semi-final success that year over Federer as he faced the on-form Swiss in a night showcase, third-round match.

But Safina, while planning to watch that encounter in person, had her own reasons to celebrate.

"There's a first time for everything," she said of her trip to the final 16. "Twice I lost in the third round. This is the third time. It should be the luckiest one."

Safina faces off at the weekend against the winner from the match between French 15th seed Alize Cornet and Daniela Hantuchova. (dpa)