(CNN) -- American Cristie Kerr leads the way after the second round of the U.S. Women's Open, after shooting a one-under par 70 at the Saucon Valley Country Club, Pennsylvania.
Kerr leads the field after 36 holes as she looks to add the 2009 U.S. Women's Open to her victory in 2007.
The 2007 champion leads fellow-American Paula Creamer by one shot after moving to a three-under-par 139 total.
Creamer, still seeking her first major championship, fired a three-under 68 to move into second place on a two-under-par total of 140.
Qualifier Jean Reynolds was the only other player to score under par after two rounds. Reynolds carded a one-over 72 to stand on one-under-par 141 after 36 holes.
Italy's Giulia Sergas carded the low round of the championship so far, a four-under-par 67 that moved her into a tie for fourth place with first-round leader Choi Na Yeon Choi, of South Korea, on even-par 142.
World number one Lorena Ochoa, who has never won the U.S. Women's Open, struggled to a second round 79 and the Mexican is now nine strokes back on six-over-par 148.
Ochoa's round included two double-bogeys, five bogeys and just one birdie. "It was just hard all the way from the beginning," Ochoa told reporters.
Meanwhile, the second round of the PGA Tour John Deere Classic was postponed due to heavy rains on Friday without a single player teeing off.
Storms and steady rain prevented the golfers from getting out on to the Deere Run course in Illinois.
Two-time U.S. Open champion Lee Janzen and Darron Stiles are tied for the lead after the opening round on seven-under 64. J.J. Henry, Matt Bettencourt and Dean Wilson are all one shot adrift of the leaders.