LANCASTER, United States (AFP) - South Korean Chella Choi, still seeking her first LPGA victory, fired the lowest third round score in US Women's Open history, a six-under par 64, to leap into contention Saturday.

The 24-year-old from Daegu made six birdies on the front side at Lancaster Country Club for a 29, the lowest nine-hole score in US Women's Open history, but missed a 3-foot par putt at 18 to match the tournament's record-low round of 63 by Sweden's Helen Alfredsson in 1994.

"I'm not thinking that much today about score," Choi said, noting she had no idea of the putt's special significance.

"I didn't know that. But now it's so exciting, (was) so close."

Choi stood on two-under 208 after 54 holes, sharing fifth after being level 55th when the day began, although leaders were still on the course.

"I made birdie a lot, so my putting was good," Choi said. "I think my shot is really good always, but before tournament I changed my putter so I have confidence. I made a birdie a lot."

Choi's new putter is a bit heavier and slightly longer and as a result, she said, "My stroke is better, easy stroke."

Choi's nine birdies were the most in a US Women's Open round since Canada's Lori Kane had nine in the second round in 1999.

Choi opened with a birdie, ran off three more in a row closing at the par-3 sixth then finished the front side with back-to-back birdies.

Five US Women's Open players previously had shot 30 over nine holes, most recently Jodi Ewart Shadoff in her first nine holes in 2013, but none had gone as low as Choi.

"I saw the score, I made 29, so I really had confidence," Choi said.

"Back nine, I take more chances. But I made three birdies."

Choi took a bogey at 11, answered with a birdie at the par-5 13th, then responded to a bogey at 15 with birdies at 16 and 17 before her closing bogey, her short putt miss ending her bid at another record.

"I think my stroke was good, but read is a little bit off. Left-to-right," Choi said.

"I try just inside, but I pushed it just a little bit left."