Sat Jul 7, 2012 8:44pm EDT "I hit a lot of good shots today, my 14 clubs worked very well," a beaming Choi told reporters after totaling 26 putts on fast-running greens. I had a birdie on the first hole and a birdie on the second hole, then I got some good vibes from there, good confidence from there. It was really fun out there. "I couldn't believe how I got eight birdies today, but I did," she grinned. I'm very happy, I'm very satisfied and I'm very excited. "It will be a lot of pressure tomorrow, but I know what I have to do and I know what I can control," she said of Sunday's final round. I cannot control winning. I just do my best. I have confidence and this is a good opportunity to be winning a U.S. Open. So I just hope to get a good warm-up tomorrow morning, go out there with my caddie and have fun. Pettersen, who won her first major title at the 2007 LPGA Championship, was dumbfounded by Choi's display on Saturday in tough conditions. Today wasn't easy. Today was kind of the biggest test," the 31-year-old Norwegian said. Na Yeon played phenomenal golf. I couldn't believe the scores I saw, to be honest. Asked how she viewed her own task on Sunday, Pettersen replied: "There's birdies out there. I think the wind is going to be a little bit less tomorrow from what I've seen. So if you get off to a hot start, hopefully put a number down early in the clubhouse, who knows? Taiwan's world number one Yani Tseng, who has claimed five of the last 10 major titles, emulated Pettersen by carding a 78 on Saturday to lie a distant 16 strokes off the pace.