The four-time major winner fired the low round of the day, a second straight four-under 66 in driving rain, to claim a one-stroke advantage over halfway co-leaders Viktor Hovland and Corey Conners, who both posted 70s at Oak Hill Country Club on Saturday.

Koepka is six-under for the championship after making light of the gruelling conditions with five birdies and just one bogey.

His LIV Golf colleague Bryson DeChambeau, the 2020 U.S. Open champion, is solo fourth at three-under after a 70, one ahead of World No.2 Scottie Scheffler (73) and English veteran Justin Rose (69).

No player outside the top-three at the halfway mark of six previous major championships staged at notoriously demanding Oak Hill has hoisted the trophy.

But Koepka is positioned to defy history and secure a third PGA Championship crown, to go with his back-to-back victories in 2018 and 2019, after continuing his resurgence two years after undergoing career-saving knee surgery.

Hovland will go out in the last group with Koepka chasing a first major win. PHOTO: Ross Kinnaird/Getty Images.

A win on Sunday would also be a third major win for Koepka in the state of New York, and also a sweet atonement for letting a four-shot last-day Masters lead slip to finish joint runner-up with Phil Mickelson behind World No.1 Jon Rahm last month.

"It would mean a lot. I think a major championship would mean a lot to anybody," Koepka said.

"To win one would be fantastic. I mean, I was just told that I think only Tiger and Jack have won three (since becoming strokeplay), so that would be pretty special to be in a list or category with them.

"Just got to go out and go play good tomorrow."

The former World No.1.will play the final round with Hovland, the 25-year-old Norwegian who continues to knock on the door of a major championship breakthrough.

Hovland played in the final group at last year's Open Championship won by Australia's Cameron Smith at St Andrews and also finished top-10 at last month's Masters.

“It would be a cool experience. Any chance you have to play in the final group in a Sunday on a major, that's pretty special,” Hovland said.

“But the mindset is just going to be, I play my own game, and obviously I want to win, but I am just going to play what I think is the right play on every single shot, and if I get beat, I get beat, but the plan is to not give it away.”

"It would mean a lot. I think a major championship would mean a lot to anybody. Just got to go out and go play good tomorrow." – Brooks Koepka.

Canadian Conners led for much of Saturday before getting caught in the lip of a bunker after failing to get out of a fairway trap on the 16th hole while holding the outright lead.

He was forced to take a penalty drop and wound up with a double-bogey six.

“I didn't make great contact there. I saw everybody looking up in the air. I did that as well. I thought it maybe skipped up. But you know, didn't see anything land and was pretty certain it was embedded there. The ball was below my feet and didn't quite adjust for that. Wish I could have that one back,” Conners said of the 16th.

Min Woo Lee remains the leading Australian, tied for 10th at one-over and seven shots off the pace following a third-round 71.

Cam Davis (71) is one stroke further back, with Smith (72) at four-over and Adam Scott (74) and Lucas Herbert (72) rounding the Australian contingent on six-over.