Ko Jin-young and Park In-bee set the stage for a South Korean shootout, firing second-round 65s to share a two-stroke lead heading into Sunday's final round of the LPGA ShopRite Classic.
World number two Ko made five of her six birdies in the space of six holes in her six-under effort at Seaview Bay in Galloway, New Jersey.
Park had seven birdies, bouncing back from a bogey at her penultimate hole, the eighth, with a birdie at the par-five ninth to grab her share of first place on 11-under par 131.
They were two strokes in front of Thailand's Patty Tavatanakit, who had six birdies in her six-under 65 for 133.
A victory in the 54-hole tournament would make Ko the LPGA's second three-time winner of the season after triumphs at Dallas in July and Portland two weeks ago.
"I had a lot of good opportunities for birdies," said Ko, who hit 15 of 18 greens in regulation and needed 27 putts. "I made a lot of really good putts, so I didn't make a bogey today. That makes me very happy and I can't wait to play for tomorrow."
She birdied three in a row starting at the par-five third, then added two more birdies at the seventh and eighth before picking up one more shot with a birdie at the par-four 16th.
"My game was perfect on the front nine, but I was thinking, OK, I want to get more birdies on back nine," Ko said.
"But I little nervous when I was thinking about that, but I had pretty good round today. Putting was good -- putting, swinging, everything was good."
A victory on Sunday would also make Ko the fifth South Korean LPGA player with 10 wins, along with Pak Se-ri, Shin Ji-yai, Park and Kim Sei-young.
World number three Park, making her first LPGA start in six weeks, opened on 10 and picked up three birdies in her first nine holes.
Birdies at the third, fourth and sixth moved her into a tie for the lead with Ko and she bounced back from her lone bogey at the eighth with a clutch birdie at her final hole.
Another impressive day on the greens for Park included her 30-foot birdie at the sixth and a six-foot par save at seven.
"I remember putting good in Kia and then earlier in the season," Park said. "And then middle of the season to the end of the season, not as good. I feel like this week is almost back to like where I was putting really good earlier in the season."
She was looking forward to dueling Ko.
"Knowing that number two player in the world is hunting for the same thing I am hunting for, definitely need to put some good performance," she said. "Good motivation to play for."
But neither of the co-leaders could afford to overlook Patty, winner of the ANA Inspiration earlier this year.
The Thai said she would go out with "no pressure, no expectations.
"I'm just going to go out there and play golf, and hopefully I get up to where I think I should be," she said.