Park, last year’s LPGA Tour Rookie of the Year, showed her growing maturity as she birdied the final three holes for a 14-under-par 202 total and a one-stroke lead over Taiwan’s Candie Kung, who had a joint best of day 67.

Helen Alfredsson, the popular 43-year-old Swede, was in second place at halfway, but she had a rollercoaster 71 – five birdies and four bogeys – and slipped back into fourth place on 10-under-par.

Another veteran, 48-year-old American Juli Inkster, who won the title in 2002, was in third place on 11 after a 69 and she could become the oldest LPGA winner if she does claim the title for a second time tomorrow.

But world number one Lorena Ochoa, who defends the women’s British Open at Sunningdale this week, dropped to six shots off the lead after a 70, and two-time former winner Annika Sorenstam was 11 strokes behind after a disappointing 73.

Park, who lives in Florida, had a career best of joint second in last year’s US Women’s Open and has had another two top fives in majors

In a third round that started in glorious sunshine and ended in rain, she staged a great birdie finale, including rolling a putt in from 10 feet at the long 18th to snatch the lead.

“I just know I have to be patient,” said Park of her desire breakthrough win.

“I played pretty mediocre at the start but told myself to not to hurry anything and it paid off.

“I surprised myself by coming back so strong. But it was great that I managed to stay so positive.”