First-round leader Maria Hjorth, Sorenstam's Solheim Cup teammate from last week, shot a 1-over 72 and is tied for second place with Michelle Ellis, who posted a 2-under 69. The duo is knotted at 6-under-par 136.
Karine Icher of France was part of the lead until late back-to-back bogeys. All totaled on Saturday, Icher shot a 1-under 70 and is alone in fourth at minus-5.
Sorenstam, already a six-time winner on the LPGA Tour in 2005, wasted little time in breaking into red figures. She knocked a pitching wedge to 8 feet at the par-5 first and drained the birdie putt.
She parred her next four, but hit an 8-iron to 7 feet at the par-3 sixth to set up her second birdie. The Swede found trouble at the eighth when her 6-iron approach missed the green. Sorenstam chipped to 12 feet, but two-putted for a bogey.
Sorenstam atoned for the mistake at the next hole. She rolled in a 22-foot birdie putt, then made it two in a row with a 4-footer at the par-four 10th.
Sorenstam came up just short of the putting surface with her 4-wood second shot at the par-5 14th. Her chip rattled the pin, but did not fall. She had to settle for a tap-in birdie and first place at 7-under par.
The 63-time winner on the LPGA Tour got to 8 under with a 20-footer at the 15th. Unfortunately, Sorenstam could not stay at minus-8 and things went south when her drive at the 17th found the rough. She had to lay up, then hit another sand-wedge to 16 feet, where she two-putted for a bogey.
Still, Sorenstam owns a one-shot lead and has been lights out with the lead heading into the final round.
'I'm very happy with the way I played today,' said Sorenstam, who went 4-1 in defeat last week for the European Solheim Cup team. 'I thought I hit the ball beautifully. I'm very pleased.
'I don't really look at how many shots I'm ahead or behind tomorrow. I'm going to go out and I want to continue to hit the ball the way I have. Under par is obviously necessary. I have improved a shot every day, so why don't I improve one tomorrow and then I'll be pretty happy.'
Hjorth had an up-and-down round on Saturday with three birdies, three bogeys and three pars on his front nine. She caught fire with a pair of 15-foot birdie putts at 10 and 11, but made a serious mess of No. 12.
Her drive landed on tree roots and she took an unplayable. Hjorth's third hit a tree and fell in the rough, then her fourth landed in a bunker. Hjorth 's fifth landed 15 feet from the stick, where she two-putted for a disastrous triple-bogey seven.
Hjorth dropped another shot to par with a two-putt bogey from 10 feet at the 16th, but got within one with a 12-foot birdie putt at the closing hole.
'It was just a bad break, it happens,' said Hjorth, referring to the triple-bogey at 12. 'Other than that, I was really happy with my round. I made a lot of putts and I played solid again.'
Ellis opened on the back nine and made the turn at even-par. She ran home a six-foot birdie putt at one, then collected back-to-back birdies at five and six.
Ellis was tied with Sorenstam, but bogeyed the eighth when she missed from five feet.
Paula Creamer, who led the United States in points last week in her debut in the Solheim Cup, managed an even-par 71 and is tied for fifth with Laura Davies, who was crushed by Creamer in the singles, and Leta Lindley. The trio came in at minus-2.
The 36-hole cut came at 7-over-par 149 and 77 players made it to the last round.