Former U.S. Open champions Paula Creamer and Park In-bee were tied for the clubhouse lead along with Mika Miyazato in Friday's second round of the LPGA Championship in Pittsford, New York.
With the Locust Hill Country Club course lined with deep, unforgiving rough, players struggled to shoot par and the co-leaders at the year's second women's major led the way with two-under-par totals of 142.
South Korea's Park, the 2008 U.S. Open winner, shot a two-under 70, while 2010 U.S. Open champion Creamer and 2010 Japan Women's Open winner Miyazato registered matching even-par 72s in the second round.
Japans' Miyazato, looking for her first U.S. win, made a highlight birdie on the par-four 13th after an hitting her second shot short of the green following an errant tee shot.
Miyazato punched a chip shot past the hole and into the green's upper tier, then watched the ball trickle back down into the hole for birdie.
On the course, three-time LPGA Championship winner Pak Se-ri and 2010 winner Cristie Kerr pushed past the clubhouse leaders during the second wave of starters.
Pak made the turn at four under par but had challenges ahead on a course where the projected cut was at five over par.
One stroke behind the leaders in the clubhouse were Hur Mi-jung of South Korea and American Sydnee Michaels.
Hur fired a 69, one of only two players among the early starters to break 70 on a day when the average score was about four over par.
Sweden's Karin Sjodin was the other player in the 60s, with her 69 giving her an even-par total of 144. Also at level par were Americans Stacy Lewis (72) and Lizette Salas (70), and Japan's Ai Miyazato (74).
(Reporting By Larry Fine in New York)