Seven-time Grand Slam champion Serena Williams battled through to the Australian Open final Thursday, staving off a determined challenge to beat Czech teenager Nicole Vaidisova 7-6 (7/5), 6-4.

Williams, who has won the title here twice before, will meet either top seed Maria Sharapova or fourth seed Kim Clijsters in Saturday's final and bid to become the first unseeded player to win the championship since 1978.

The 25-year-old American was overjoyed as she continued a remarkable comeback from a long injury lay-off that has seen her world ranking slip to 81, although the Australian Open run will put her back in the top 20.

"I'm really excited, I've got nothing to lose, I'm having fun, back into the top 20, that means so much to me," she said.

Williams had to fight hard for the win as her 17-year-old opponent staged a late comeback which the 2003 and 2005 Australian champion showed qualities similar to her own.

She said she feared choking as the Czech stormed back into the match but hung on to claim victory in one hour 46 minutes.

"Almost did a gag-arooney there," Williams said after the match. "She played some incredible points on match point, she just got relaxed, she reminded me a little of myself.

"I just tried to stay focused and tried to stay calm."

Vaidisova came into the game vowing not to be intimidated by Williams and gained a huge confidence booster when she broke her opponent in the first game with her aggressive returns from the baseline.The teenager was not afraid to play her shots, hitting cross-court winners and wrong-footing Williams a number of times.

Knowing she could not afford the slow starts that have marred an otherwise stunning return to form at this tournament, Williams broke back after attacking Vaidisova's second serve.

She was a picture of steely concentration facing her young challenger, showing none of the roller-coaster of emotions that have been on display on her previous outings in Melbourne this year.

Vaidisova rode her luck when a booming forehand hit the net on break point but deflected onto the line, allowing her to edge ahead of Williams.

But the Czech's nerves emerged in only her second Grand Slam semi-final when she netted the ball on set point, while Williams retained her composure to again break back and the first set went to a tie-break.

Williams romped to a 5-1 lead but two double faults allowed Vaidisova back in to level the tie-break 5-5.

The former champion regathered to reach set point with a shriek of relief then converted the chance when Vaidisova again slammed the ball into the net.

She seized the momentum with two early breaks, with Viadasova breaking back only to gift Williams a break with two double faults.

Williams seized the opportunity and raced away to a 5-1 lead before Vaidisova staged a late fightback to claw her way back to 5-4, saving four match points in the process

She should have lost on a fifth match point but her return was incorrectly called in and Williams was powerless to question the decision as she had run out of challeges that allow a player to use the HawkEye system to check calls.

With her mother Oracene gesturing for her to remain calm, Williams made no mistake on the sixth match point and kept alive her dream of a fairytale return to Grand Slam tennis.

Provided by AFP.