Danielle Kang fired five birdies during a 4-under 68 Friday to move into a tie for the 36-hole lead with New Zealand's Lydia Ko at the Gainbridge LPGA at Boca Raton, Fla.
Ko held the first-round lead on the strength of a 63, but she slowed down Friday with a 70, matching Kang at 11 under for the tournament at Boca Rio Golf Club. They lead Jodi Ewart Shadoff of England (69) and Yuka Saso of Japan (70) by four shots.
Kang won last week's event, the Tournament of Champions, and continued her run of good form by pairing birdies on Nos. 8-9 and 13-14.
Kang and Ko, who are good friends, will play in the final threesome with Shadoff on Saturday.
"She's like my little sister, and I think everybody knows that," Kang said of Ko. "She had a phenomenal round yesterday, shot 9-under, and I just saw that she was at 11, so I just kind of wanted to get to double digits today.
"I was starting off at 7 and this golf course is tough. You know, 3-under is a good score, 4-under is a good score, so just wanted to post going to score today."
Ko had an up-and-down round, following a birdie at No 3 with a bogey at No 7 and another birdie at No 9 with a bogey at the 11th. Birdies at No 14 and 17 allowed her to wrap up on a positive note.
"More of a grind than yesterday," Ko said. "When you get off to a hot start I think you do put a little bit of pressure. Even though you're a couple under par you don't feel like it was as good because you keep comparing. But I tried to not do that and be committed over each shot and play the best golf I can today."
In colder conditions, the course played much tougher during the second round. Switzerland's Morgane Metraux had the round of the day, a 6-under 66 with eight birdies and two bogeys. There was only one 67, a bogey-free card from France's Celine Boutier.
Metraux is tied for fifth with Japan's Nasa Hataoka (71), India's Aditi Ashok (72) and Englishwomen Bronte Law (70) and Charley Hull (71) at 6 under. Boutier is part of a large tie for 10th at 5 under that includes major champions Brooke Henderson of Canada (71) and Patty Tavatanakit of Thailand (68).