Defending champion Serena Williams [Images] beat world number four Svetlana Kuznetsova 3-6, 7-5, 6-3 to reach the Sony Ericsson Open final on Thursday.

Williams will play world number three Jelena Jankovic in Saturday's final after the Serbian overpowered Russia's [Images] Vera Zvonareva 6-1, 6-4 in the other semi-final.

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Former world number one Williams, who was struggling with back trouble in the hot and humid conditions, is bidding to equal Steffi Graf's [Images] record of five Miami [Images] titles.

The American had been practically flawless in her last-eight victory over world number one Justine Henin [Images] but made 43 unforced errors against Kuznetsova.

"I felt I made a lot of errors compared to the quarter-final," Williams told reporters. "Svetlana played an entirely different game than I expected her to play, but once I got used to it I was okay."

Twice in the first set -- after the fifth and seventh games -- Williams was on the ground receiving treatment on her back from the trainer.

"It got better once the trainer came out," Williams said. "The first time she (came on the court), she did something that worked.

"It got stuck out of nowhere, but once she fixed it, it got better."

SERVICE BREAKS

Kuznetsova, who had beaten Williams's sister in the last eight said: "I like playing both of them. I played better against Venus."

Three of the first four games of the match were decided by service breaks with Kuznetsova gaining the upper-hand at 3-1.

Serving at 0-40 in the fifth game, Kuznetsova hit a crafty drop shot on the line that turned the game around for her and she went on to take a 4-1 lead.

"I think if I played the right points at the right time I could've won it in two sets," Kuznetsova said.

"When I was on top of the game I played too safe. When she was on top, I was playing better. It's uncomfortable this situation because I thought I was playing well."

Williams patiently waited out the second set where she finally scored a service break in the 12th game at 15-40 when Kuznetsova crashed an easy overhead into the net.

Both players struggled to hold serve in the deciding set amid the blistering conditions.

Kuznetsova surrendered her serve in the eighth game after dumping a backhand into the net, putting Williams in a position to serve out for the match.

The American thumped down an ace to set up match point and then Kuznetsova sailed a backhand long.

Jankovic's march to the final is fairly remarkable considering she was nearly knocked out of the tournament in her first match, staving off five match points to overcome a 1-5 deficit in a deciding set against Sofia Arvidsson of Sweden.

"I'm really excited to be in the finals here for the first time," Jankovic said. "I think I played some good tennis tonight.

"Can you imagine? I could have been out already in (my) first round."

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