Brittany Lincicome, who is chasing her first USLPGA title since 2011, posted a one-under 71 to maintain the lead at the LPGA Championship.
The American on Saturday finished 54 holes at Monroe Golf Club at 10-under-par 206, with former world number one and defending champion Park In-Bee and Norway's Suzann Pettersen a shot back on 207.
Lincicome, who started the day with a three-shot lead, admitted the pressure of defending that advantage hit her shortly before the round began.
"Nervous was probably an understatement," she said. "I was fine all morning. I got my 10 hours of sleep. Then when it came time to kind of eat lunch, it just wasn’t happening."
But Lincicome's four birdies out-numbered her three bogeys. She said the nerves dwindled as the day progressed.
"Hopefully going into tomorrow it's kind of out of my system," she said. "I kind of know what it feels like to be in this position and I will dominate again."
Lincicome, a five-time winner on the LPGA Tour is trying to become the fourth consecutive American to win a major this season, joining Lexi Thompson (Kraft Nabisco Championship), Michelle Wie (US Open) and Mo Martin (British Open).
Her resume already includes a major title at the 2009 Kraft Nabisco, but her last win came three years ago at the ShopRite Classic.
South Korea's Park kept Lincicome in her sights with a third-round 69, while Pettersen, the 2007 LPGA Championship winner, posted a 67.
Pettersen powered home with four birdies on the back nine.
"I made the turn a bit frustrated that I three-putted nine," Pettersen said. "I actually got to the green and three-putted, which felt like I was giving away a shot. But I managed to kind of make a move ... it's nice to make a charge and be where I'm at right now."
Park claimed the last of her four birdies at the 17th before closing her round with a par.
"I hit a couple of bad shots and kind of scrambled around today," she said. "But number 17 and 18, dropping those putts really helped me for tomorrow. Three back is quite a bit different, so I'm happy where I am right now."
South Korea's Lee Mi-Rim (69), who won last week at the Meijer Classic, was alone in fourth at seven-under par.
New Zealand's Lydia Ko (71), Gerina Piller (69) and Meena Lee (71) were tied for fifth on six-under 210.
Ko, seeking a first major title at the age of 17, could overtake Stacy Lewis atop the world rankings with a win this week.