Novak Djokovic saved two match points against Roger Federer to win a thrilling US Open semifinal.

This is the second year running that Djokovic came back from match point to defeat Federer.

Federer played in an attacking style which helped him win the first two sets. However, Djokovic came back to win 6-7 (7-9) 4-6 6-3 6-2 7-5.

The world number one is standing one win from a fourth Grand Slam title. If he wins, it will be his third of an already extraordinary 2011 season.

Earlier, rain had delayed the match for almost an hour and a half. But the wait was worthwhile.

The first set was extremely tense with no break points. Finally, it was Federer who cut loose to win it in a tie-breaker.

The second set saw Federer play with utmost confidence he had gained after winning the first set tie breaker.

He played a few exquisite backhand shot to get the first break in the second set. In game six, Djokovic broke back only to see that he had to face another break of service immediately. A few minutes later, Federer took the second set. The Serbian looked like going home.

But Djokovic had other intentions. He played with focus in the third set to win it after breaking Federer's service.

Djokovic again broke Federer at the start of the fourth set and suddenly it appeared that he was back in the game. He raced through the fourth set by breaking Federer again.

The fifth set saw Federer take the initiative to break the service of Djokovic to take a 5-3 lead. Federer served for the match. At 40-15 with 2 match points with him it seemed like the Swiss was going to make it to the final. But Djokovic proved why he is the current best. He broke back. From then Federer was in the back foot.

Djokovic won the next three games to clinch a sensational win.