Sophie Gustafson, who shared the second-round lead with Sorenstam and Paula Creamer, managed a 2-under 70 and is alone in third place at 8-under-par 208.
Stacy Prammanasudh posted a 5-under 67 on Saturday to move into fourth place at minus-seven.
Michelle Wie, who was disqualified after last year's final round in her professional debut, birdied her closing hole for an even-par 72. She is tied for 13th place at plus-2.
The Swede flew out of the gate on Saturday with a pair of birdies at two and three, a feat she has accomplished in each of the first two rounds. She parred four and five, but assumed the top spot on the leaderboard thanks to back-to-back birdies at six and seven.
Sorenstam bogeyed the ninth hole, which was an improvement from Friday's second round when she double bogeyed the par-4 hole. She recovered the lost stroke at 10 and was one ahead of the field.
At the par-5 12th, Sorenstam seemed poised to cash in from 6 feet, but missed the putt left. Gustafson sank a 35-foot eagle putt at the 12th to get one behind, but Sorenstam drained a 40-foot birdie putt at 13 to move to 11 under par, two clear of Gustafson.
Sorenstam was strong with the irons at 14 and 15, but missed birdie putts inside 10 feet at both holes. Gustafson took a big gamble going for the green in two at 15 and her second landed in the water. She made bogey and Sorenstam was three in front.
Then Ochoa, a four-time winner this season, made her move up the leaderboard. She tallied three birdies on her front nine, but parred eight consecutive holes around the turn.
Ochoa, who won last week in her native Mexico, birdied the par-5 15th to get to three back. She sank a long birdie putt at the 18th to close the gap to two, but unfortunately for Ochoa, Sorenstam was still on the course.
At the par-4 closing hole, Sorenstam knocked her approach 12 feet over the flag. The Swede ran home the birdie putt to extend her margin to three over Ochoa.
'I was a lot more settled today. I felt a lot more comfortable,' said Sorenstam. 'I was figuring out a few key thoughts to have today and it seemed they worked.'
Sorenstam can reach a few milestones if she is to hang on Sunday afternoon.
A win would be her 70th on the LPGA Tour and put her 18 behind the all-time record. If she visits the winner's circle, Sorenstam will become the first player in tour history to win the same event six times. Sorenstam has another chance at win No. 6 in an event when she goes to the Mizuno Classic next month, an event she won five times in a row, which is already an LPGA Tour record for most consecutive wins in the same event.
If she is to win another money title of Player of the Year honor, she will have to stare down her playing partner in Sunday's final round.
'I'm looking forward to the day,' said Sorenstam. 'I've always enjoyed Lorena. She's having a super year. I think it's going to be exciting tomorrow and I'm in good position.'
For Ochoa, she may need to finally topple Sorenstam in the final round to eliminate any doubts. In Ochoa's four wins on tour this season, Sorenstam was in the field for only one.
'I like to be paired with her in the last group,' said Ochoa. 'I'm going to come tomorrow, be aggressive, be very positive. I know I can do this. I'm going to give her a hard time.'
Creamer only shot an even-par 72 and is tied for fifth place with Cristie Kerr (68) and reigning Women's British Open champion Sherri Steinhauer (71). The trio is knotted at 6-under-par 210.
Seon-Hwa Lee, who has already clinched Rookie of the Year honors, and Pat Hurst both shot rounds of 1-under 71 and are tied for eighth place at minus- 3.
Nabisco Champion Karrie Webb struggled to a 3-over 75 and is alone in 10th at 1-under-par 215.