US star Lexi Thompson fired a bogey-free six-under par 65 to stretch her lead to three strokes after Friday's second round of the LPGA Kingsmill Championship.
Thompson stood on 12-under 130 for 36 holes at the 6,430-yard Williamsburg, Virginia, layout with compatriot Gerina Piller second and world number one Lydia Ko of New Zealand sharing third on 134 with Taiwan's Candie Kung.
Fifth-ranked Thompson, one stroke in front of Piller when the day began, charged ahead with a birdie at the par-5 third and added birdies at the par-4 sixth and par-5 seventh, then closed the front nine with another birdie.
She added birdies at the par-4 14th and par-3 17th to pad her lead entering the weekend.
Piller stumbled late to fall back but matched Thompson's strong start with a birdie at the par-5 third, then three birdies in a row starting at the ninth. She made another at the par-5 15th but bogeys at 16 and 18 sandwiched around a birdie at 17 kept her off the pace.
Ko, trying to fight off rivals and remain atop the rankings, fired a bogey-free 67, opening with a birdie on the par-4 10th, adding back-to-back birdies at the par-5 third and par-4 fourth and another at the par-5 seventh.
"Playing well. Was good to get confidence going into the weekend," Ko said. "It was a pretty steady round. The front nine I gave myself a lot of looks for birdies and a lot of them really slipped by. But I feel like I'm putting good strokes on it. That's all I can do at the end of the day."
South Korea's Chun In-Gee and American Vicky Hurst shared fifth on 135 with China's Feng Shanshan and Americans Angela Stanford and Brittany Lincicome on 136.