PINEHURST, June 21, 2014 (AFP) - Wie had a 36-hole total of four-under par 136, and was the only player under par when she walked off the course.
By the end of the day, she was three strokes clear of 19-year-old compatriot Lexi Thompson, who also posted a second-round 68 at Pinehurst for a one-under par total of 139.
World number one Stacy Lewis shared third place after a 73 for 240. She was tied with Australian amateur Minjee Lee, who carded a 71, and South Korean Amy Yang who posted a 69.
"End of the day yesterday, I was thinking if I just did this again, that would be nice," Wie said.
"Finishing with two birdies is always great," the American added. "It's a grind out there. It's not easy. Really grateful for the par putts that I made and some of the birdie putts that I made. I can't complain. I'll take it."
Thompson teed off on 10 and rebounded from a bogey at 18 with three birdies in a row at three, four and five.
"Today went very well for me, I stayed within my routine and went one shot at a time," Thompson said. "That's what the US Women's Opens are all about, you just have to stay patient.
"There's not as many birdie holes on this golf course," Thompson added of Pinehurst No. 2, where the world's top men battled in the US Open last week.
"Out here you have to put your ball on certain parts of the greens and take your par and be happy with it. Sometimes out here even bogeys are good."
Lewis, the defending Women's British Open champion, has already posted two wins this season at the North Texas LPGA Shootout and ShopRite Classic.
But she found the going tough on Friday, with her three birdies countered by six bogeys.
- Lewis welcomes challenge -
Even so, the American welcomed the challenge heading into the weekend.
"I like it when you have to hit good shots and think your way around the golf course," Lewis said. "The USGA will keep switching things up, and I think it's fine when they make the golf course harder.
"I think being four shots back on a hard golf course is a good place to be."
Schoolgirl Lucy Li's week as the youngest player ever to qualify for the US Women's Open ended as the 11-year-old posted her second-straight 78 to miss the cut.
The diminutive Californian, whose family is from Hong Kong, found some positives to take away, especially in her ability to rebound from tough holes.
At the par-four 13th, she was in some dense weeds off the tee and missed the ball as she tried to hit out.
She ended up with a triple-bogey, her second of the tournament.
But the sixth-grader responded with a birdie at 14.
"I'm really happy with how I bounced back from the big numbers," Li said.
Leading second-round scores on Friday in the US Women's Open golf championship at Pinehurst (USA unless noted, a-denotes amateur, par-70):
136 - Michelle Wie 68-68
139 - Lexi Thompson 71-68
140 - a-Minjee Lee (AUS) 69-71, Amy Yang (KOR) 71-69, Stacy Lewis 67-73
141 - Choi Na-Yeon (KOR) 71-70
142 - Paula Creamer 70-72, Mariajo Uribe (COL) 72-70, Sakura Yokomine (JPN) 74-68
143 - Angela Stanford 71-72, Stephanie Meadow (NIR) 71-72, Karrie Webb (AUS) 70-73, Ryu So-Yeon (KOR) 69-74
144 - Sue Kim (CAN) 71-73, Catriona Matthew (SCO) 75-69, Jenny Shin (KOR) 74-70, Feng Yue Er (CHN) 73-71, Azahara Munoz (ESP) 73-71, Gerina Piller 72-72 Pornanong Phatlum (THA) 71-73, a-Brooke MacKenzie Henderson (CAN) 71-73
145 - Chella Choi (KOR) 75-70, Mina Harigae 71-74, Katherine Kirk (AUS) 69-76, Meena Lee (KOR) 72-73, I.K. Kim (KOR) 71-74, Pak Se-Ri (KOR) 76-69
146 - a-Mathilda Cappeliez (FRA) 76-70, Lee Jee-Young (KOR) 73-73, Misuzu Narita (JPN) 76-70, Jennifer Song 74-72, Park Hee-Young (KOR) 73-73, Julieta Granada (PAR) 75-71, Ji Eun-Hee (KOR) 71-75, Sandra Gal (GER) 74-72, Juli Inkster 71-75, Danielle Kang 75-71