Brooks Koepka carded a flawless five-under-par 67 to claim a commanding four-shot advantage after the penultimate round of the CJ Cup at Jeju Island in South Korea.
The three-time major winner was able to negotiate a tricky few opening holes before kickstarting his third round with back-to-back birdies around the turn.
He collected further gains at the 14th, 17th and 18th to move to 13 under overall ahead of the final 18 holes, with Ian Poulter and halfway leader Scott Piercy his closest challengers.
Graeme McDowell carded his best round of the week with a bogey-free 69 which included birdies at the sixth, 15th and 18th to move into a tie for 21st at four under par.
Koepka will have his sights set on a fifth PGA Tour title on Sunday — and, remarkably, his first in a non-major since February 2015 when he triumphed at the Phoenix Open.
Ryder Cup star Poulter has an outside chance of clinching his second title of the year after birdies at three of his final four holes.
Poulter, who triumphed in Houston in April after defeating Beau Hossler in a play-off, bounced back from his only bogey on the fourth hole with a birdie on the ninth.
He thrived on the back nine thanks to further birdies on the 12th, 15th, 16th and 18th which helped him card a four-under 68.
Piercy sits alongside the Englishman after an eventful level-par 72, in which he followed up five birdies with as many bogeys.
Spain's Rafa Cabrera Bello is among six players who sit on eight under, while former world number one Jason Day lies a shot further back.
Paul Casey will have his sights set on at least a top-10 finish after shooting up the leaderboard with a six-under 66 on Saturday.
Collated third round scores in the The CJ Cup at Nine Bridges, Nine Bridges Country Club, Korea (South) (USA unless stated, Irish in bold, par 72):
203 Brooks Koepka 71 65 67
207 Ian Poulter (Eng) 70 69 68, Scott Piercy 70 65 72
208 Pat Perez 72 68 68, Cameron Smith (Aus) 74 67 67, Gary Woodland 73 67 68, Rafael Cabrera-Bello (Spa) 73 70 65, Chez Reavie 68 70 70, Jamie Lovemark 72 68 68
209 Jason Day (Aus) 73 71 65, Ted Potter, Jr. 77 67 65, Ryan Armour 73 67 69
210 Brendan Steele 74 71 65, Paul Casey (Eng) 71 73 66, J.J. Spaun 71 70 69, Si Woo Kim (Kor) 69 73 68
211 J.B. Holmes 73 70 68, Hideki Matsuyama (Jpn) 71 74 66, Ryan Palmer 72 70 69, Keith Mitchell 75 69 67
212 Kevin Na 73 69 70, Alex Noren (Swe) 74 65 73, Graeme McDowell (NIrl) 71 72 69, Sung Kang (Kor) 75 67 70, Austin Cook 70 75 67
213 Shubhankar Sharma (Ind) 74 75 64, Andrew Putnam 73 68 72, Tyrrell Hatton (Eng) 72 73 68, Louis Oosthuizen (Rsa) 72 71 70, Brice Garnett 73 69 71
214 Charley Hoffman 76 71 67, Beau Hossler 75 70 69, Adam Hadwin (Can) 71 71 72, Emiliano Grillo (Arg) 73 75 66, Joel Dahmen 72 70 72, Abraham Ancer (Mex) 75 71 68, Dong Seop Maeng (Kor) 71 73 70, Joaquin Niemann (Chi) 75 70 69, Ernie Els (Rsa) 73 71 70, Marc Leishman (Aus) 75 71 68, Patton Kizzire 71 72 71, Kevin Tway 73 72 69
215 Nick Watney 70 74 71, Justin Thomas 73 70 72, Adam Scott (Aus) 75 69 71, Kyle Stanley 72 72 71, Jason Dufner 72 72 71, Cheng-Tsung Pan (Tai) 76 69 70, Brian Harman 76 64 75, Sungjae Imn (Kor) 73 71 71
216 Peter Uihlein 73 71 72, Rod Pampling (Aus) 70 73 73, Danny Willett (Eng) 69 77 70, Brandt Snedeker 72 72 72
217 Charl Schwartzel (Rsa) 76 70 71, Byeong-Hun An (Kor) 70 77 70, Brian Gay 74 70 73, Branden Grace (Rsa) 75 73 69, Kevin Chappell 76 71 70, Tae Hee Lee (Kor) 72 71 74, James Hahn 76 69 72, Jimmy Walker 72 69 76, Ryan Moore 72 73 72
218 Brian Stuard 77 68 73, Kyoung-hoon Lee (Kor) 78 73 67
219 Sang Hyun Park (Kor) 75 73 71, Billy Horschel 74 74 71, Stewart Cink 77 69 73, Charles Howell III 72 76 71
220 Whee Kim (Kor) 76 75 69, Doyeob Mun (Kor) 72 80 68, Xander Schauffele 76 73 71, Chesson Hadley 75 73 72
221 Hyungjoon Lee (Kor) 74 72 75
222 Jason Kokrak 77 73 72
225 Michael Kim 70 75 80
227 Min Chel Choi (Kor) 82 72 73
228 Hyun-woo Ryu (Kor) 77 76 75
