West Australian Hannah Green remains on course to defend her LPGA title in Portland but she will have to do it by chasing down the leader on the final day.
Going into day two of the shortened Cambia Portland Classic as the co-leader, Green carded a four-under 68 at Columbia Edgewater Country Club to move to 10 under.
But she gave up top spot on the leaderboard to England's Mel Reid, who fired a blemish-free seven-under 65 to celebrate her 33rd birthday.
Green had six birdies on Saturday, including one at the opening hole and one on 18 courtesy of a sinking a lengthy putt, but dropped shots at the 2nd and 10th holes.
"It was definitely slower than yesterday," Green said.
"I got off to such a great start, so always hard to back up a low round.
"Really happy with my last putt. Holed a long bomb there, so gives me another positive momentum for tomorrow.
"Hopefully, I can get the pace of the greens a little bit better and give myself opportunities."
The birdie also gave the 23-year-old Green – whose first LPGA win was last year's Women's PGA Championship winner – sole possession of second place.
Reid – chasing a maiden LPGA win – was full of confidence after her fine round that has her 12 under in the event reduced to 54 holes because of poor air quality caused by wildfires.
"Put myself in a great position, a position that everyone wants to be in, so I'm excited for the opportunity tomorrow," Reid said.
"Just keep doing the same thing and see where tomorrow afternoon takes us."
Reid said she has postponed her birthday celebrations for a day.
"Celebrations will start tomorrow no matter what for my birthday." Reid said.
"I've got to be well behaved tonight and I was well behaved last night, which is shocking to many people."
Korean Amy Yang (66) and Amy Olson (68) were tied for third at nine under.
"I love being in contention. It's so fun," Olson said.
"It's what we play for, what we practice for."
Georgia Hall (66), Celine Boutier (67), Yealimi Noh (69) and Gaby Lopez (69) were a shot further back in a tie for fifth.
Green's fellow Australians Sarah Kemp (71) and Minjee Lee (74) are even par and made the cut on the number.