Ochoa led by as many as four shots, but needed a 25-foot bogey putt at the 18th hole for a 3-under 69 and a three-round total of 12-under 204. Pettersen made five birdies in a seven-hole stretch to post the third-best round in tournament history, an 8-under 64.
Ochoa and Pettersen will be paired Sunday in the final round, just seven days after squaring off in a playoff at the Longs Drugs Challenge. Pettersen beat Ochoa in the playoff last Sunday for her third win of the season.
Ochoa, the defending champion, will be looking for her seventh win of the year.