BRISBANE (REUTERS) - Maria Sharapova rallied to beat Kaia Kanepi today and will meet Serena Williams in the Brisbane International semi-final knowing she must drastically improve to end her run of 13 straight defeats against the world No. 1.

Williams comfortably beat Slovakian Dominika Cibulkova 6-3, 6-3 in 61 minutes, winning the first set without losing a point on serve.

Prior to this match, Sharapova was involved in an error-strewn battle as she came from a set down to defeat Estonia's Kanepi 4-6, 6-3, 6-2 in two hours.

Had 2012 champion Kanepi been in better form - the match produced 66 clangers in total - the Sharapova-Williams semi-final match-up the tournament organisers had been hoping for would have been scuppered.

The Russian did improve as the match went on and, in the third set, her service accuracy improved to 84 per cent, nearly double her efforts in the first two sets.

"You're going up against a great champion that's playing great tennis at the moment," Sharapova said.

"You know that you have to raise your level in order to beat her. I think the intensity level of our matches are always high. I think she goes up and wants to play the best tennis against me."