The Serbian was again in remarkably fine fettle for a man who has not played a tournament since making a successful defence of the Australian title nearly five weeks ago and, after three solid wins already, raised his level once more in a 6-3, 7-6 (7-4) success over the Argentine.

Djokovic was made to do so.

Del Potro hit some fierce first serves and some heavy ground strokes mixed in with thunderbolt accelerations with his forehand, advancing to a 3-0 lead in the second set. He then broke back stridently for 5-5 when it looked as though the match was lost.

Djokovic responded superbly when he was behind, containing brilliantly, moving superbly, and counter-attacking with excellent timing and accuracy.

He faltered for the second time in three matches when trying to close the contest out, but repaired the damage with a typically tenacious effort in the tie-break. It earned him his 55th final.

"I am proud of that record and of what I have done in my career," he said. "It's been more than successful and I am trying to cherish every moment I spend on a tennis court.

"Juan Martin was very powerful, and when I was behind I needed to hang in there. I knew it was only one break and that I could pull it back."

The first set offered few hints of the struggle to follow. Djokovic broke through in the sixth game at the first attempt, and closed out the set without fuss.

But in the second set Del Potro began to rally more sternly and found moments of inspiration to launch stunning drives, sometimes for clean winners.

His early lead brought a great response from Djokovic, elevating some of the rallies to an outstanding level.

Djokovic's break back to 2-3 came amidst a gale of boos and jeers, though none of it was directed at the Serbian. Instead it was created by the umpire's decision to impose a time violation on Del Potro when he took a little longer to prepare at break point down.

The Argentine walked up to the umpire to protest, gesticulating as he did so, and accompanied by a spate of noises from spectators. By the time the situation had calmed, the delay was at least twice the permitted 25 seconds.

There followed a forehand-to-forehand exchange ending with a mishit under pressure by Del Potro costing him his advantage. When they sat down there was another exchange between the umpire and Del Potro, with another jeering accompaniment from spectators.

It appeared to have been a turning point. Extra pressure was now on the Argentine and although he diligently saved two more break points amid a sequence of excellent rallies in his next service game, Djokovic was too good.

Playing somewhere near his best, he contained brilliantly and struck some trenchant forehand counter-drives, one of which earned a third break point and another which converted it, to reach 5-3. But as against Bautista Agut he surprisingly did not close out the match.

Del Potro saved a match point with a fine first serve to reach 4-5 and then attacked well when Djokovic failed to get first deliveries in.

The tie-break was tense and tight until Djokovic found a backhand down the line which opened up the court for a piercing forehand down-the-line winner. That made a mini-break of serve, which eventually proved the decisive moment.

Djokovic was due to play the winner of Roger Federer, the defending champion, and Tomas Berdych, the conqueror of Federer in their last meeting at the US Open in New York in September.

Later Del Potro criticised umpire Magdi Somat for his handling of the time violation incident.

"It's very important point for the game, for the match. Maybe he doesn't know about that, you know, " he said. "I mean, in that moment, if you call warning or if you do something different, you can lose the focus and that's what happened with me."

Del Potro had Djokovic's support.

"I don't know exactly if the chair umpire gave him (Del Potro) an unofficial verbal warning before that. If he didn't, then I don't agree with that decision," Djokovic said.