Suzann Pettersen carded a 4-under 68 on Friday to take the lead at the U.S. Women's Open, the third major on the LPGA calendar.

Pettersen, who was a runner-up to Paula Creamer at this event in 2010, finished 36 holes at 5-under-par 139.

"I like the U.S. Opens," said Pettersen. "It's usually the biggest test of golf throughout the year. I like the way the USGA sets up the courses. They make it tough. They make it fair. And it's by far one of my favorite championships, just because of that."

She mastered the tough Blackwolf Run course Friday, and is just one stroke ahead of two Americans -- Cristie Kerr and Michelle Wie, who share second at minus-4.

Kerr, one of three first-round leaders, is in pursuit of her third major championship and second U.S. Women's Open title, having won in 2007. She carded a 1-under 71 on Friday.

Wie's presence at the top of the leaderboard is a mild surprise when placed within the context of her season. The 22-year-old has missed the cut six times and hasn't finished inside the top-30 all year.

Still, Wie is a two-time winner on the LPGA and owns six top-5 finishes in major tournaments. Her 6-under 66 on Friday immediately pulled her into contention.

Inbee Park, the 2008 winner, shot a 2-under 70 to reach minus-3. She shares fourth place with Sandra Gal (70) and Vicky Hurst (70).

Missing from the top of the leaderboard are the top two players in the world, Yani Tseng and Stacy Lewis, who are part of a large group tied for 29th at plus-2. Lewis managed a 3-under 69 to rebound from a poor first round, while Tseng carded a round of even-par 72.

Pettersen began her round at No. 10 and immediately got into red figures, with a birdie on her opening hole. She carded three more birdies in her next six holes to get to minus-5, and hadn't even reached the turn.

The Norwegian's momentum slowed on the front nine, where she parred the first three before stumbling to a bogey at the fourth. But she got that stroke back with a birdie at No. 8, then parred her last.

"This year there are birdies out there," said Pettersen. "I probably shouldn't say this, because we come out tomorrow and they'll probably make it impossible. But the course is playable. So just keep sticking to the game plan."

Wie took advantage of the playable conditions. She also started on the back nine and birdied her first two holes, then reached 4-under for the round with birdies at 14 and 15.

"Yesterday I had a lot of 40-foot putts, 50-foot putts," Wie said. "Today on the back nine I had a lot of putts within 15 feet. That really helps on the golf course. It's the difference between lagging them and trying to make them. So I was putting them in good positions today."

Wie went further under par on the front nine, where she birdied her first. A bogey at the next hole dropped her back, but she rolled in birdies at four and six to reach minus-4.

She parred out to complete the 66, which is her best round at a U.S. Women's Open by three shots. It's also her second round below 70 this year.

Kerr began at the first tee and carded one birdie during a clean front nine. She bogeyed the 11th, but birdied two more holes to get under par for the round.

The veteran Kerr has bogeyed just one of her 36 holes so far, a remarkable run when so many others have found struggles.

"Just a very important round for me," said Kerr. "One that said I wanted to keep up that consistency, and I did that today. Even though I had some adversity in the middle of the round, I was able to bounce back from that."

Heading into the weekend, the leaderboard is fairly crowded toward the top, with 12 players separated by four shots.

Lizette Salas, one of the first-round co-leaders, shot a 73 to slip to minus-2. She shares seventh with Mika Miyazato (71).

American teenager Lexi Thompson (73), Na Yeon Choi (72), Nicole Castrale (70) and Il Hee Lee (71) are tied for ninth at 1-under 143.

Friday was a struggle for Brittany Lincicome, who was tied for the lead heading into the second round. She posted an 8-over 80, and made the cut on the line at 5-over 149.

Defending champion So Yeon Ryu (71) is part of a large group in 17th at plus-1.

NOTES: Morgan Pressel withdrew Friday. She played 14 holes during her second round, carding a 10 at the 14th, before opting out of the tournament. A runner-up at the 2005 U.S. Women's Open, Pressel has been struggling with a thumb injury lately. The ailment forced her to withdraw from last week's Walmart NW Arkansas Championship...Among those to miss the cut are 2005 champion Birdie Kim (158) and Juli Inkster (161). A two-time U.S. Women's Open winner and Hall of Famer, Inkster was playing her second event since coming back from an injury.