Melbourne: Defending champion Novak Djokovic saw off brave Andy Murray in five thrilling sets Friday to reach the Australian Open final and stay on course for his third straight major title.

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In a marathon match of 4hr 50min, nudging the tournament record, the Serbian top seed stormed back from a set down to win 6-3, 3-6, 6-7 (4/7), 6-1, 7-5 and set up a final with Rafael Nadal on Sunday.

"There's not any words that can describe the feeling I have now," Djokovic said. "Andy deserves the credit to come back into the match after 2-5 down. He was fighting, I was fighting."

Djokovic, 24, now gets a shot at his third Australian Open title while Murray extends his quest for Britain's first male grand slam title in 76 years.

But the Scot took pride in his turnaround from last year's final, in which he was floored in straight sets by the Serb.

"Tonight's match was important for many reasons," he said. "Obviously I wanted to win first and foremost.

"But also after last year, the year that Novak's had, I think there's a very fine line between being number one in the world and being three or four. I think that gap, tonight I closed it."

The rollercoaster match of long rallies, with 155 unforced errors and 18 service breaks, came down to a gripping fifth set in which Djokovic drew first blood, breaking in the sixth game to take a 4-2 lead.

But the Scot refused to buckle, thrillingly breaking Djokovic as he served for the match at 5-3 and sending the packed Rod Laver Arena crowd into a frenzy.

Murray levelled at 5-5 with a service hold and then had three break points to move ahead, but he let the crucial opportunity slip through his fingers.

It left the Scot needing to hold serve to stay in the match but he slipped to 15-40, and a forehand on the stretch into the net saw Djokovic over the line and into the final.

"It was one of the best matches I've played, but emotionally and mentally it was hard," Djokovic said. "I felt like we were breaking each other's serves easier than serving it out."

"I'm going to try to recover but obviously it's going to be physical as well, so I need to do some push-ups tonight," he added.

The start of the match gave no clue as to the drama to follow, with Djokovic breaking Murray twice to seal the first set and forcing an early break in the second as the Scot struggled to gain a foothold.

But in a statement of intent Murray, an Australian Open finalist in 2010 and 2011, produced a leaping overhead at the start of game four and stepped up a gear, levelling the set at 2-2.

It proved a turning point as the fired-up Scot found his best form, holding easily and then breaking again before taking the second set.

The British number one stayed in charge in a gruelling third set lasting 88 minutes, nearly the same as a football match, as he dictated the points with the Serb struggling to hold serve.

Murray saved three set points on his serve and then dominated the tie-break to move ahead.

But just when the top seed looked in real trouble, there was a momentum shift, with Djokovic racing into a 4-0 lead in the fourth set with two breaks, taking it 6-1 to set up the dramatic decider.

The match lasted 4hr 50min, not far short of the longest ever played at the Australian Open, the 2009 semi-final between Rafael Nadal and Fernando Verdasco, which lasted 5hr 14min.

Djokovic, who enjoyed one of the greatest seasons in tennis history in 2011, is bidding to become just the fifth man to win three consecutive grand slam titles in the open era when he faces Nadal.

"What can be a bigger challenge than playing against Rafael Nadal, one of the greatest players ever," the Wimbledon and US Open champion said. "We're great friends off the court and have lots of respect for each other."