Novak Djokovic has reached the US Open final after coming from two-sets down to beat Roger Federer.

There was little to seperate the competitors in the first set, and it needed a tie-break for Federer to win 9-7.

The number three seed fired into a two-set lead when he dispatched the out-of-sorts Serbian 6-4.

Djokovic began his comeback by claiming the third set 6-4, before showing the form which has put him at the top of the world rankings with a 6-2 victory in the fourth.

In a tense final set, Federer squandered two match points before Djokovic broke back to serve out the final set 7-5 and seal a dramatic win.

Djokovic will face Rafael Nadal in Monday's final after the Spaniard beat Andy Murray in four sets.