Taiwan's Yani Tseng, who is seeking her second consecutive LPGA Tour victory, fired a three-under 69 to seize a three-shot lead after three rounds of the Kia Classic.
World number one Tseng had a bogey-free round to reach 12-under 204 heading into the final round at the La Costa Resort and Spa course. The 23-year-old Tseng is also gunning for her third title in five tournaments this year.
South Korea's Jiyai Shin was second at nine-under 207 after a 68.
Sun Young Yoo, of South Korea, and Caroline Hedwall were seven under 209. Yoo had a 67 and Hedwall, of Sweden, made a bogey on the 18th to post a 70.
Tseng managed to save par with an eight-foot putt on the par-four 18th.
She earned her 14th career LPGA Tour title by capturing the LPGA Founders Cup last week in Phoenix. Tseng also won the LPGA Thailand event in February. She led the LPGA last year with seven victories, including the Women's British Open.
Tseng has won five of the last six times she has held a 54-hole lead. She is 6-5 overall in her career with the lead heading into the fourth round.
Tseng, who had a 67 and 68 in her opening two rounds, birdied the par-four first hole and also birdied the par-five seventh and 12th.
Shin finished with seven birdies and three bogeys. She birdied the first three holes, and got within one shot of Tseng with another birdie on No. 6.