World number one Park In-Bee of South Korea closed with back-to-back birdies in a round of six-under par 65 on Saturday to move into contention at the LPGA Northwest Arkansas Championship.
Park, who will be chasing history next week at the US Women's Open after winning the year's first two women's major titles, moved within two strokes of the lead after 36 holes in the 54-hole, $2 million final tuneup for the Open.
Japan's Chie Arimura also closed with back-to-back birdies to fire a 65 to grab a share of the lead with US world number two Stacy Lewis, Spain's Beatriz Recari and South Korean Ryu So-Yeon on 10-under 132 at Pinnacle Country Club.
Park was in a pack in fifth on 134 that also includes compatriots I.K. Kim and Oh Ji-Young plus Thailand's Pornanong Phatlum.
New Zealand amateur Lydia Ko, the 16-year-old reigning US Women's Amateur champion who won an LPGA title last year in Canada, was on 135 along with Japan's Mika Miyazato, who led after day one but followed a 65 with a 70.
As much as Park is going for the $300,000 top prize and her fifth title of the year, she is preparing for next week's major event at Southampton, New York.
Park, 24, won the Kraft Nabisco Championship in April and this month's LPGA Championship and with a US Women's Open triumph, she would match Babe Zaharias from 1950 as only the second player in LPGA history to win a season's first three majors.
While there were only three LPGA majors 63 years ago, Park would need three more wins to complete an LPGA Grand Slam -- the US Women's Open, which she captured in 2008 for her first major title; the Women's British Open, where she was runner-up last year; and the Evian Championship, a first-time major in France where she is defending champion.
"I'll probably start thinking about it once I get to next week," Park said. "Next week is a big week for me. I don't want to force anything. I want everything to happen naturally. This week is a good week for me to get ready for next week. I will just go out there tomorrow and do my best."
Park birdied three of the first five holes before closing the front nine with her only bogey of the day. She followed with birdies at the par-3 11th, par-5 14th, par-3 17th and par-5 18th.
"I really liked the way I played," Park said. "I didn't miss many greens. I didn't miss many fairways. I could have made more putts. The putts have got to fall some time."
Lewis, a former University of Arkansas player receiving home-area hero support this week, seeks her third title of the year while last-pair partner Recari seeks her second crown of the season.
Defending champion Ai Miyazato of Japan fired a bogey-free 64 to stand on 137, inspired by her friends being among the leaders after an opening 73.
"I played well and had a lot of fun. I had a great memory from last year," she said. "My friends are playing well this week. That was inspiring. I kept watching the scoreboard and was thinking, 'I have to get playing good too.'"