Pak, widening her lead with an eagle on the hole she double bogeyed a day earlier, shot her second consecutive 4-under 68 Saturday to take a three-stroke lead over Sorenstam after two rounds of the 54-hole tournament.
Sorenstam, who came from 10 shots back on the last day to win last year, was second at 5-under 139 after a 68.
Laura Diaz, whose 69 left her four shots behind Pak, will be the third player in the final threesome on Sunday.
Pak is pleased to be playing the last 18 holes with Sorenstam.
'I always want to play with the best players to get better,' the South Korean star said. 'She's such a great player and I'm working to play as well as she does. I'm not going to try too hard and push myself too much tomorrow, though.'
Sorenstam, sounding a bit intimidating, said she intended to play aggressively.
'Hopefully I will be paired with her (Pak) so I can put pressure on her,' the 31-year-old Swede said before the final group was set for the last round. 'I hope I get off to a good start with birdies, but it will depend on what she does.
'I will be able to see what she does close up. I will know exactly what she does, and if I need to play more aggressively. I have come here to win, not to be tentative.'
Sorenstam also noted that players behind them are still a threat. That would include Diaz, whose victory two weeks ago in Tucson, Ariz., was her first on the tour.
Michelle Estill, whose lone LPGA win came in her rookie year of 1991, had a 70 that left her five shots behind Pak.
The 24-year-old Pak, the LPGA's rookie of the year in 1998 and winner of 13 titles - including three majors - in her brief career, is playing her third event of the year and looking for her first 2002 win.
She realizes she is not yet regarded as being on the same level as Sorenstam and 27-year-old Karrie Webb, the tour's dominant players in recent years, but believes she's getting close.
'I'm younger than them and haven't played long enough on the LPGA,' Pak said. 'The best thing is for me to work as hard as I can and do the best I can and someday soon I will be at their level.'
The first-day leader in the tournament at El Caballero Country Club, Pak seemed to be faltering during the second round when she hit her tee shot into a bunker and bogeyed the 160-yard, par-3 16th.
She quickly regained her composure.
On the 463-yard, par-5 No. 17, where she had hit in the water and three-putted from 11 feet for a 7 the previous day, she hit a good drive, stroked her 9-iron onto the fringe 18 feet from the pin, then rolled in the winding putt for an eagle 3.
Pak finished the round with five birdies - after having seven the first day - and the lone bogey.
Sorenstam tied Mickey Wright's 37-year-old LPGA record for overcoming the biggest final-round deficit in a victory when she came from 10 shots back with a 66 last year. Sorenstam overtook struggling leader Pat Hurst, who shot 77, then beat Mi Hyun Kim on the first hole of a playoff.
That 2001 tournament was played on a different course, Wilshire Country Club, but Sorenstam, who has won twice this year and has 33 career victories, seems entirely comfortable playing at El Caballero, which is in suburban Tarzana.
Like Pak, Sorenstam also had five birdies and one bogey during the second round.
Sorenstam is coming off her fourth win in a major, successfully defending her title in the Kraft Nabisco Championship.
Pak, however, has been steady when she's leading on the final day. She has been in front 11 times to begin the final round and won all but two of those, finishing seventh once and third another time. Sorenstam has come from behind to win 11 of her 33 titles.
Wendy Doolan, tied with Tonya Gill one shot behind Pak after the first round, shot 74 to fall seven shots behind. Gill had a 75. Webb was in a group at 1 over after a 71.
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