CARLSBAD, Calif. (AP) _ Second-seeded Maria Sharapova used her strong serve to defeat Patty Schnyder 7-5, 6-4 on Saturday to advance to the finals of the Acura Classic.

Sharapova's dominance on her serve was also the key to her winning the second game of the second set, which lasted 24 points and took more than 15 minutes to complete.

``I think I served smart,'' said Sharapova, ranked No. 4. ``That was probably the greatest thing about my serving. I was consistently smart. I mixed up it up good and mixed up the pace good.''

Sharapova will meet either top-seeded Kim Clijsters of Belgium or No. 7 seed Nicole Vaidisova of the Czech Republic, who played Saturday night in the other semifinal. Clijsters, ranked No. 2, will attempt to extend her 23-match winning streak in North American summer hardcourt tournaments.

Sharapova has yet to beat Clijsters in four career matches, and has never played the 17-year-old Vaidisova. Sharapova reached her fourth final this season, but has won just once at Indian Wells in March.

The fifth-seeded Schnyder and Sharapova each held serve for most of the first set, although they did it in different fashions. Sharapova, one of the WTA Tour's better servers, allowed just six points on her serve in the first set. Schnyder had to struggle to hold her serve, but did so as the pair were on serve at 5-5.

That's when Sharapova converted the only break point of the first set. Sharapova hit a forehand winner off a short ball to take a 6-5 lead. She then served out the set.

``I didn't do too good at the beginning. She won her serve too easy,'' said the eighth-ranked Schnyder. ``She has a huge serve. Each and every point she's like 100 per cent concentrated and focused. She really never gives you a breath. Just a really complete player.''

Sharapova, the 2004 Wimbledon champion, kept her momentum from the first set by breaking Schnyder's serve in the first game of the second set. Then came the long second game, with the Russian staving off five break points and featuring a total of nine deuces.

On three of Schnyder's break points, Sharapova's big serve caused Schnyder to hit weak service returns for easy points.

Sharapova took a 2-0 lead by winning that game, then jumped out to a 5-1 lead before Schnyder closed it at the end. Schnyder scored her only service break of the match to cut the lead to 5-3, then held serve before Sharapova won the match when Schnyder hit a backhand wide.

Schnyder, playing in her third straight semifinal, lost last week to Clijsters in the finals of the Bank of the West Classic at Stanford, Calif.