World No.5 Lee, the LPGA Tour's leading scoring this year, shot a three-under 69 on a day Upper Montclair Country Club showed some teeth with the wind picking up early and rain falling on the leaders on the back nine.
The 25-year-old from WA, who had a three-shot lead overnight, was at 17-under 199 after 54 holes. She's looking for her first win of the year and seventh on tour.
She leads from Sweden's Madelene Sagstrom, who had the first-round lead after a 63 and had the best third-round with a 67. The 29-year-old is seeking her second win.
Entering the week with a scoring averaging of 69.167, Lee tied for second in the HSBC Women's World Championship in March and shared third in the Los Angeles Open last month.
She retains the lead thanks to an eagle-birdie on putts ranging from 15-to-18 feet on the 12th and 13th holes on Saturday.
"You know, I've been striking it really well pretty much this whole year," said Lee. "I've been working hard on my putting and working hard on everything, so it would be really nice just to see the result of a win."
Lexi Thomson started the round tied with Sagstrom at 11 under, and was alone in third, three shots back after a 69. She might have been closer to her first win since 2019 but she just missed at least five or six putts.
"The weather was a big factor, it got quite wet on the greens," said Sagstrom, who briefly moved into a tie for the lead with a birdie at the par-5 12th as Lee bogeyed No. 11 after an errant tee shot.
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