ROME (AFP) - World No. 1 Novak Djokovic overcame a self-inflicted ankle injury to battle into the Rome Masters final after a thrilling 2-6, 6-4, 7-6 (7-5)win over Kei Nishikori on Saturday.

The Serb will meet Britain's Andy Murray, the second seed, in a second successive Masters final on Sunday a week after beating the Scot in Madrid.

Djokovic, the top seed and defending champion, had laid the foundations for a fifth title in Rome with a hard-fought and classy win over seven-time champion Rafael Nadal on Friday.

But he almost scuppered his hopes when he inadvertantly bruised his left ankle with his racket as he hit it against his shoe to shake off the red dirt.

Later, he said: "A message to all the kids out there - don't hit your own ankle when you're cleaning your shoes."

If left him requiring medical treatment, and appeared to rob him of the early momentum against the Japanese sixth seed.

"It was an awkward situation in the first game, I hit myself pretty hard on the ankle and bruised the bone," he explained. "It hurt for a while, and though the pain faded it returned towards the end of the match."

Nishikori - who suffered a semi-final defeat by the Serb in Madrid - was a tough customer for tennis' man of the moment.

Nishikori's agility and movement were crucial in a 43-minute first set that he peppered with a healthy dose of drop shots.

Djokovic upped the momentum at a key moment in the second set, forcing a decider with a break on his first set point in the 10th game. He maintained the momentum in the third set, but again Nishikori came out swinging.

The Serb got the break in the second game, only for the Japanese to level at 4-4.

He saved match point at 5-4 before going on to force the tiebreak. Although he saved a further two match points, Nishikori was unable to save a fourth as Djokovic sealed the win in just over three hours.

In the end, the Serb won 112 points to 111 for Nishikori.

"The first set was flawless from his side, and in the third set he had a couple of break points," said Djokovic.

"Maybe a couple of opportunities I could have done better. But big credit to Kei. I saw the stats, I only had one more point than him and that says everything."

Nishikori said: "I'm really disappointed, it was only a matter of a few points in the tie break.

"I played really good and aggressive in the first set, and in the second I stopped doing that and his game got better.

"I think in the tie break I made too many unforced errors. That was the biggest mistake I made today."

Djokovic will now meet Murray on Sunday, the second time in a week the pair have featured in a Masters final.

Murray had an easier path to the final, winning his semi-final over French lucky loser Lucas Pouille in just over an hour.

"I'm excited to go out again and battle. I don't have too much time to recover, but I've had this situation before in my career," added Djokovic, aiming for a fifth Rome title.

Meanwhile, three-time champion Serena Williams said she can't wait after setting up the first all-American women's clay-court final in 14 years.

She will meet Madison Keys on Sunday.

The last time two Americans faced off in the final of a WTA clay-court event was in 2002, when Williams beat her older sister Venus to win her maiden French Open at Roland Garros.

Williams, who will aim for her fourth and second successive title in Paris in a fortnight, said: "You know, we're an all-American final on the clay. That's just - it's great. It's really exciting."