World number one Lydia Ko surged into a share of the halfway lead with a five-under-par 66 in the second round at the Marathon Classic in Sylvania, Ohio on Friday.
Ko gathered six birdies in a testing breeze on the Highland Meadows course to join South Korean Kim Hyo-joo (68) at eight-under 134, one stroke ahead of American Alison Lee and South Korean Jang Ha-na, with Ariya Jutanugarn of Thailand among a trio two shots back.
American Brittany Lang, winner of the US Women's Open on Sunday, shot 69 to trail by five strokes.
Lang captured the Women's Open after third-round leader Ko faded in the final round with a 75.
But the South Korean-born Kiwi sounded philosophical about her inability to close out what could have been a third major victory in four starts.
"Hopefully I get in that position again," she told reporters and asserted, "I didn't feel that down or disappointed. There were just so many positives to take from it. Every week is a new week (and in) this wind (today) I feel like my score is a pretty solid one."
Former child prodigy Michelle Wie continued her recent poor play to miss the cut after shooting 69 77.