- USGA Photo

Kim edged first round leader Lydia Ko, 15, of New Zealand, by a single stroke at the 6,512-yard, par-72 course at The Country Club.

Starting her round on the second nine on Tuesday, Kim birdied five of the first seven holes for a nine-hole score of 31. She was 1-over-par on the first nine for a score of 37-31–68.

“I really played well on my front nine, but for the other nine I had a couple of mistakes,” Kim said through an interpreter. “I made the five birdies because I saw where I should aim it and it was exactly right. My irons were close to the hole.”

Kim has a one-stroke lead over Ko, who was at 7-under par after the first five holes of her second round. Ko opened play on Monday with a 6-under-par 66. She is the top-ranked player in the Women’s World Amateur Golf Ranking, was co-medalist at the 2011 U.S. Women’s Amateur and finished as the low amateur at last month’s U.S. Women’s Open.

Sierra Brooks, 14, of Sorrento, Fla., who won the 2010 U.S. Kids Golf World Championship, fired a second-round 68 for a 36-hole total of 4-under 140.

At three-under are Paula Reto, 22, a native of South Africa who is a senior at Purdue University, and Minjee Lee, 16, of Australia, the 2012 U.S. Girls’ Junior champion. Reto added a 68 to Monday’s opening round of 73, while Lee had a 69 to go with her 72 on Monday.

After the stroke-play rounds conclude on Tuesday evening, the field will be cut to the low 64 scorers for match play. At "virtual press" time, it appeared that a playoff among players that shot 151 would determine the last few match play spots. Matches will continue throughout the week with a 36-hole final scheduled for Sunday.