Despite shooting just a one-under-par 71, Sorenstam shares the lead at six-under 138 after two rounds of the 20-player event at Bighorn Golf Club.

The defending champion, Sorenstam recorded six birdies - including the 18th - but also bogeyed three holes and double-bogeyed the par-four ninth.

Sorenstam shares the lead with fellow Swede Sophie Gustafson and American Paula Creamer. Gustafson had six birdies and four bogeys en route to a 70, while Creamer registered five birdies and just one bogey, at the ninth, in her round of 68.

Sherri Steinhauer is one shot off the pace at five-under 139 after firing a bogey-free 67, the round of the day.

Karrie Webb (69) and first-round co-leader Lorena Ochoa (73) are two shots back.

While Sorenstam is looking for a historic win, Michelle Wie is back and looking for her first, but she has a lot of work to do.

Wie, who turned 17 on Wednesday, followed up a two-over 74 with an even-par 72 and is tied for 15th, eight shots off the pace.