Smith shot a second successive five under 67 at Shoal Creek to forge a dominant advantage at 10 under overall after the Australian completed her round before a near three-hour delay for bad weather, which ultimately forced play to be halted early.
"I knew from the start it was going to be tight, " said Olesen, who entered the final round tied with Molinari one stroke behind Lee Slattery. He's pretty - he always has a good thing to say to keep you on track. Still, there was candid reflection of events from the 10th after which she was "scared" to hit tee shots.
Kim rallied from a seven-shot deficit with nine holes to play to force a playoff with Jutanugarn, who finished regulation with back-to-back bogeys.
Jutanugarn looked almost invincible during Saturday's third round when she made her move into the lead with a 67, powering through the soggy Shoal Creek course easily. "When you are leaving them short, that's because of nerves".
"I have nothing to lose", said Smith. Lincicome said Friday at the U.S. Women's Open that she was asked to play in the Barbasol Championship in Kentucky July 19-22.
She made a almost ideal bunker shot to within a foot of the cup on the tournament-clinching hole, beating South Korea's Hyo-Joo Kim, who shot a 5-under 67 in the final round to force the playoff.
The top two finished four shots clear of Solheim Cup star Carlota Ciganda, whose five-birdie 69 ensured her best finish in a major, and there was another four-shot gap to last year's KPMG Women's PGA champion Danielle Kang.More news: U.S. states declare emergency ahead of subtropical storm
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A victory by Ariya would end the recent domination of South Koreans and Americans, who have claimed the past 11 U.S. Women's Opens. Kim had a birdie on the first hole in the two-hole aggregate playoff but gave back a shot with a bogey on the next hole.
Seven shots in front, nine holes left.
"I felt pretty good", Jutanugarn said of facing that decisive sand shot. "I didn't sleep much last night and I'm really exhausted. I just want to go out and be proud of myself every day", Jutanugarn said.
"I've not been in this position before (in a major), but I feel comfortable on the greens here and hope tomorrow (Saturday) is like another day at the office".
She has a way to go, but nonetheless took delight at seeing her name atop the leaderboard the entire round.
She had reason to feel tired as she had set her alarm for 4 AM local time, after not realizing that the morning resumption had been pushed back an hour from its originally scheduled time of 6:45 AM.
Not only that, Smith, who is winless in 222 starts on the LPGA Tour, got to sleep in on Saturday while many of her rivals were up before dawn.