The Swedish star had four birdies and three bogeys on the Tokyo Yomiuri Country Club course to take a 9-under 207 total into the final round. Japan's Kaori Suzuki was second after a 69.
'My driving was excellent, but I had a hard time getting the ball to the hole,' Sorenstam said. 'The wind was tough to judge on several holes and that made it hard to reach the pin.'
Sorenstam, set to face the men in two weeks in Fort Worth, Texas, picked up her first birdie of the day on the 500-yard, par-5 sixth hole when she chipped on from the side of the green and sank a 7-foot putt.
Sorenstam's first bogey of the round was on the par-4 10th, where she three-putted. She picked up a stroke on the par-4 14th with a 15-foot birdie putt, but missed a 2-foot par putt on the short par-3 15th for her second bogey of the day.
'I've bogeyed that hole twice now and there's no reason for that because I'm using a nine iron,' Sorenstam said.
She came back with a birdie on the 16th when she hit a sand wedge to 8 feet and then made it back-to-back birdies after chipping to 3 feet on the par-5 17th.
'The key on this course is the par 5s,' Sorenstam said. 'I birdied two of them today and hopefully I can birdie all of them tomorrow.'
A bogey on the par-3 18th was typical of the difficulty Sorenstam had with her short game and the windy conditions. Her drive with a 4-iron landed a foot short of the green. She chipped on but left herself an uphill 30 foot putt and then two-putted.
'I hit the ball well,' Sorenstam said. 'But there was a big gust of wind and I ended up 30 yards short.'
Despite the big lead, Sorenstam wasn't completely satisfied with her game and headed to the practice tee after the round.
'I need to work on my chipping and putting,' she said. 'It didn't seem like I could score well today so I'm going to have to work on that.'
Sorenstam, who won 13 worldwide events last year, was sixth last week in the Michelob Light Open in Virginia, and has one victory in five starts this year. She will become the first woman to play on the PGA Tour since Babe Zaharias in the 1945 Los Angeles Open.
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