The American missed an opportunity to stretch her lead when she missed a two-foot birdie putt on the par-5 17th in Phoenix on Friday (Saturday AEDT).

But this was not a day to complain on the Cattail course at Whirlwind Golf Club. She followed a great 63 in the opening round - something Lydia Ko failed to do - with a steady diet of birdie chances and a smooth, confident stroke with the putter.

"I have left a couple of shots out there at the end," Korda said. "But I'm playing really solid golf, and when I do make a mistake, I try not go let it faze me too much."

She was at 16-under 128, two shots ahead of a familiar face. Hyo Joo Kim, the defending champion in Phoenix, won last week at the Founders Cup by holding off Korda in the final hour. 

Kim, who opened with a 61, overcame mistakes early to post a 69. Saturday (local time) will be the fourth straight round for Korda and Kim to play in the same group.

"Just getting sick of each other now," Korda said with a laugh. "Yeah, she's playing such solid golf. At the end of the day, that's something that motivates me; to want to stay with her at that level."

Ko shot a 60 in morning conditions of the first round and doesn't feel as though she played that much differently - except that the putts turned away at the last second or burned the edge. 

The New Zealander made so many putts in her opening round, and only enough on Friday for a 71 that left her three shots behind, along with Jenny Bae (65) and Minami Katsu (66).

The final hole summed up her day - a good drive, a good approach, and a 12-foot putt that looked good all the way until it peeled away to the right.

"I just didn't really hole many putts today," Ko said. 

"It's obviously harder to get closer to the pins, just playing in the afternoon and the greens being a little firmer."

Karis Davidson is the leading Australian, following up a first-round 69 with a 66 on Friday to be tied for 13th place at nine-under.

Compatriots Robyn Choi and Cassie Porter are both seven-under at the halfway point, tied for 35th.