Sharapova, the defending tournament champion, struggled with her serve at times against the third-seeded Kerber but prevailed 6-3, 2-6, 7-5.
Sharapova will face China's Li Na, the No. 2 seed who topped American qualifier Bethany Mattek-Sands 6-4, 6-3. Li served three aces and won 68 percent of her first-service points.
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