Serena Williams ended Amelie Mauresmo's hopes of grabbing the year-end number one ranking by beating the Frenchwoman 4-6, 7-6, 6-4 in the semi-finals of the WTA Tour Championships in Los Angeles on Sunday.

On Monday, Williams will face Wimbledon champion Maria Sharapova in a rematch of their final in London after the Russian overcame a shaky first set to ease past compatriot Anastasia Myskina 2-6, 6-2, 6-2 in the second semi-final.

Coming back from a set and a break down, the American played a gutsy and more mentally sound match than Mauresmo, who failed to convert 12 break points in a nail-biting third set.

Playing in front of a pumped-up crowd in her hometown, the emotional Williams won the two-and-a-half hour contest with a leaping overhead and jumped up and down to roars of approval.

Mauresmo needed to win the tournament to snatch the number one ranking from American Lindsay Davenport and, although she stood toe-to-toe with the six-time Grand Slam champion throughout the match, could not come up with the big shots when it mattered.

"She went for it," said Mauresmo, who lost for the eighth time in nine matches against Williams.

"To give her credit, I was playing well and she really raised her level a lot. I felt like I forced her to play her best level and make some unbelievable shots."

Trailing 1-3 in the second set, Williams held serve than broke back to 3-3 when the Frenchwoman double faulted.

The pair served well for the remainder of the set before Williams stepped up her level in the tiebreaker, winning the last five points with a series of huge groundstrokes.

Mauresmo, who has never won a Grand Slam and has admitted to choking away big matches, had numerous opportunities in the third set, but could not gain control.

In the fifth game, she held four break points but committed a backhand error and then watched Williams send down three service winners.

The Frenchwoman held another break point in the sixth game, but Williams crunched a forehand crosscourt winner.

Williams then converted her only break point of the set in the next game when she forced Mauresmo into a forehand error and held on for the rest of the match to claim victory.

"It was intense," said Williams, who ripped 53 winners to 24 from Mauresmo.

"Amelie was playing some good shots and it was hard because she changed her game.

"She was coming to the net more and taking a lot of pace off, which is a good thing to do. Then I decided to go for it and get my shots down the road."

COACHING WARNING

Sharapova had lost to Myskina in their three previous meetings, but after a shaky first set, the 17-year-old blasted her weary opponent off the court.

The Wimbledon champion was given a warning for coaching in the fifth game of the second set at 30-30, after her father Yuri was clearly heard yelling instructions at her.

"He always coaches her," Myskina said. "Most of the coaches tell you to do something in the match."

Sharapova said she could not hear what her father was saying.

"I usually don't want to communicate, but sometimes I let my emotions out," she said.

"It's not the coach who's playing out there. I always play by instinct and do the opposite of what people tell me to do."

At Wimbledon, Sharapova stunned two-time defending champion Williams 6-1, 6-4, although the American said she never showed up.

"I don't know who that was, but I wasn't at Wimbledon this year," Williams said.

Sharapova was confused by the comment.

"In reality there was one, but she might not have been in reality," Sharapova said.