MIAMI - Serena Williams extended her dominance of Maria Sharapova on Thursday, defeating the Russian 6-4, 6-3 to reach the final of the Miami hardcourt tournament for the ninth time. World number one Williams will be seeking her second straight Miami crown when she takes on Australian Open champ Li Na who booked her spot in the final of the combined WTA and ATP event by beating Dominika Cibulkova 7-5, 2-6, 6-3.

The 32-year-old Williams is the top seed and Li is No. 2 but their head to head record is one-sided in favour of Williams, who has won 10 of 11 career meetings and hasn't lost a match to Li in six years. "She brings some good game," Williams said of Li. "She comes to the net, and I'm enjoying that right now."

Sharapova, ranked fifth in the world and seeded fourth, seized the first break in each set against Williams, but couldn't build on that as she went down to the American for a 15th straight time. Williams leads their career head-to-head 16-2, and Sharapova's two victories in the rivalry came back in 2004, when a precocious 17-year-old Sharapova beat Williams in the finals at Wimbledon and the WTA Championships.

Sharapova gave herself plenty of chances to reverse almost a decade of futility, breaking Williams once en route to a 4-1 lead in the opening set only for Williams to roar back, winning five straight games to take the set. "I knew that I could play better," Williams said of keeping her composure in the face of the big deficit. "I knew I could pick it up a level."

After breaking for a 2-0 lead in the second, Sharapova took a 40-15 lead on her own serve, but Williams chipped away and gained the break to put the set back on serve. She broke Sharapova at love for a 4-3 lead, and broke her again to seal the victory after an hour and 37 minutes. For Sharapova it was another disappointing finish in Miami, where she has reached five finals but never lifted the trophy.

"I was up in a lot of the games and didn't win them today," she said. "The first set I started off really well and I had more break points. She served her way out of trouble on those in the first set. Yeah, I was in it and then I was not." In Thursday's second semi-final, Li improved to 7-0 against 11th-ranked Cibulkova. World number two Li hit two aces but she won 46 of 79 first serve points in the two hour, 20 minute match.

Li won despite hitting six double faults and taking just eight of 29 points on her second serve. Li is 3-0 against Cibulkova this year. She beat Cibulkova in the Australian Open final in January to claim her second career Grand Slam title, and downed the Slovakian again at Indian Wells earlier this month.