Cristie Kerr carded a 9-under 63 to climb into second place at 11-under-par 133. Defending champion Se Ri Pak is two strokes further back at minus-9. Lorena Ochoa, the 2003 LPGA Tour rookie of the year, heads a group at 8-under-par 136. She is joined there by Donna Andrews and Shi Hyun Ahn.
Michelle Wie used a 5-under 67 to move to 5-under-par 139, where she stands alone in 13th place.
'I don't think I hit my shots as good as yesterday, but I was definitely putting a lot better,' Wie said. 'The bogeys I made were just stupid mistakes. I felt really bad about them, but I made a lot of birdies.'
Sorenstam opened three strokes behind overnight leader Kim Saiki. The Swede nearly holed her second shot at the par-4 third and kicked in her birdie try. Sorenstam then knocked a wedge to 10 feet for birdie at the sixth.
She came back with an 11-footer for birdie on No. 9 and dropped in a three-foot birdie putt at the next to make it two straight.
Sorenstam dropped her third shot to the par-5 13th some 13 feet from the cup. She sank that birdie putt to get to minus-10.
At the par-3 17th, Sorenstam rolled in a 22-footer for birdie and came right back with a short birdie putt at the last to grab the overnight lead.
'I'm very happy. I thought I played good today,' Sorenstam said. 'I putted really good today and I hit good iron shots close to the pin and I'm very pleased. A little more tidy today than yesterday, so it was a good thing.'
Kerr, who began her day on the back nine, drained a five-foot birdie putt on No. 11, her second, to get her round going. She ran off three straight birdies from the 13th, all from within 10 feet, to move to 6 under for the event.
The 26-year-old knocked her third shot to five feet to set up birdie at the par-5 second. She sank a pair of birdie putts at the fourth and fifth to move to 9 under.
Kerr stuck a lob-wedge within two feet of the cup at the seventh for a birdie and closed out her strong round with a four-foot birdie putt at the ninth to grab second place.
'I played really well,' Kerr said. 'This is probably one of the best ball striking rounds I've had, and I switched to a new putter last Sunday. It just felt really good, and I just started making putts.'
Saiki struggled to a 1-over 73 Friday. She shares seventh place at 7-under-par 137 with Grace Park, Karen Stupples, Laura Davies and Heather Bowie. Lorie Kane is one stroke further back at minus-6.
The cut line fell at 2-over-par 146 with 82 players advancing to the weekend.