Serena Williams and Mardy Fish with the Hopman Cup in Perth on Friday. (AFP)

Perth: The United States edged out an injury-hit Serbia in a deciding mixed doubles to win a dramatic Hopman Cup final on Friday.

The US led 1-0 after Jelena Jankovic forfeited her singles against Serena Williams because of a leg injury.

World No. 3 Novak Djokovic shrugged off fatigue to pull Serbia level with a battling 6-2, 6-7, 7-6 victory over Mardy Fish.

Jankovic returned for the mixed doubles but the US hit back from 1-4 down in the first set to win it 7-6, 6-2 and clinch their fifth Hopman Cup title.

The day had begun with disappointment for the fans inside the Burswood Dome when Jankovic, who suffered a leg injury earlier in the week, handed former world No. 1 Williams a walkover.

That left Djokovic with the task of trying to keep the final alive and he did just that, after winning an epic battle against Fish.

The Serb, who almost single-handedly helped Serbia reach the final, raced through the first set against Fish, breaking twice to take it in just 29 minutes.

Fish twice led by a service break in the second set, at 2-1 and 4-3 but on both occasions, Djokovic broke straight back.

The Serb looked set to wrap it up when he forced a match point on the Fish serve at 5-4, but the American held on and then snatched the tie-break 7-4.

Djokovic had treatment on his right shoulder at the start of the third set and looked to be fatigued thereafter, but he held firm to take the deciding tie-break 7-4 when Fish sent a forehand return wide.

Jankovic took to the court with the top of her right thigh heavily strapped but it looked like Serbia may win their first Hopman Cup title when they stormed to a 4-1 lead in the first set.

Fish and Williams hit back to level at 4-4 but Serbia had four set points on Fish’s serve in the 10 game only for the US to hold on and then take the tie-break 7-5.

That seemed to break the spirit of the Serbs and after breaking for 4-2, the US repeated the feat two games later to clinch victory (Reuters)