Korda fired a four-under 67 for the second straight day at Riviera Country Club to move to six-under 207 and set herself up to claim her first Open crown and fourth major title overall.
Having dominated The Chevron Championship in April, Korda is looking to go one better at the 100-year-old country club in Pacific Palisades after finishing runner-up at the Open in 2025 at Erin Hills.
Korda was seven shots off the lead after her opening-round 73, but she got into contention with Friday's lowest score before surging steadily up the leaderboard on moving day.
"It's always amazing to be in this position," Korda said.
"That's what we work so hard for, to be in this spot. So whatever happens tomorrow happens, but I'm going to give it my all and see what the outcome is."
Korda chipped in from the fringe for birdie on the third hole on Saturday, and then slotted an 18-foot birdie putt on the sixth.
She finished with her birdie spree, reaching the par-five 17th green in two before smashing her 154-yard approach shot to four feet on the 18th.
"I think last year I really, really wanted it, and the more you want it, sometimes the more you stiffen up and you get a little bit more nervous," the 27-year-old said.
"I play my best golf when I'm happy, free Nelly and I'm kind of joking around out there. That's kind of the attitude that I'm going to have (Sunday)."
Kim shot 68 with one birdie over the last three holes to keep pace with Korda while fellow American Jennifer Kupcho (69) and South Korea's In Gee Chun (69) share third place, one shot behind.
Gold Coast's Karis Davidson (71) remains on track for a career-best finish in a major championship after a late fightback in round three, topping the four-strong Australian contingent who made the cut.
Starting the round four strokes off the lead, Davidson, who was the final player added to the field, was left to rue two poor holes that have given her a six-stroke deficit to make up in the final round.
Three-time major champion Minjee Lee hit just seven greens in regulation in her four-birdie round of 71 and will start the final round in a share of 34th at three over while Grace Kim is in a tie for 40th.
Hannah Green's eagle from 10 feet at the par-five first was the only real highlight of a disappointing campaign that sees the one-time major winner in a tie for 46th at five-over.
Ruoning Yin (71) of China is in a tie for fifth while the other second-round co-leader, Alison Lee, struggled with five bogeys while also making four birdies and shot 72.
American Lee, who gave birth to son Levi 15 months ago, would be only the fourth mother to win the US Open and the first since Juli Inkster in 2002 but her bogey on 18 knocked her into a tie for eighth at three under.
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