Serena Williams stormed into the final of the WTA hardcourt tournament at Stanford on Saturday, winning the last eight games of a 7-5, 6-0 victory over Andrea Petkovic.

The world number one and top seed, playing her first tournament since a disappointing Wimbledon campaign in which she was slowed by a virus, will face third-seeded German Angelique Kerber in Sunday's final.

Kerber, ranked eighth in the world, saved a match point on the way to a 4-6, 7-6 (7/4), 6-2 victory over 59th-ranked American Varvara Lepchenko.

Petkovic, 26, who ousted 34 year-old Venus Williams in the quarter-finals on Friday, pushed 32 year-old Serena hard in the opening set as they battled through the first 11 games without a break of serve.

After holding for a 6-5 lead, Williams turned the tide in the 12th game, although she needed a fifth set point against Petkovic's serve to gain the break and the set.

There was no stopping the 17-time Grand Slam champion from there. After a first set lasting 50 minutes Williams polished off the second in 27, breaking Petkovic a fourth time when the German sent a forehand long on match point.

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