Brooks Koepka in lead at Oak Hill as he goes for PGA Championship hat-trick

Koepka, winner of back-to-back PGA Championships in 2018 and 2019, sparkled in tough, rainy conditions at Oak Hill on Saturday, mixing five birdies against a single bogey for a four-under 66. That put the American at six-under 204, one clear of Canada's Corey Conners and Norway's Viktor Hovland.

A win Sunday "would mean a lot," said Koepka, who has four major wins on his resume already. "I was just told only Tiger and (Nicklaus) have won three, so that would be pretty special to be in a list or category with them."

While a PGA Championship hat-trick would be impressive, Koepka would still have work to do to pass Woods, who has four trophies and Nicklaus five.

Conners, bidding to become the first Canadian man to win a major since Mike Weir two decades ago at the Masters, had held steady atop the leaderboard for much of a turbulent day when a double-bogey at the 16th knocked him from his perch.

Until then Conners had put in a disciplined error-free effort getting to two-under with three holes to play. But his ball became plugged in the deep rough on the lip of a greenside bunker and the 31-year-old dropped two shots for a level par 70.

Hovland was in position to join Koepka at the top but a bogey at the last denied the world number 11, who also signed for a 70.

Conners and Hovland had shared the second round overnight lead with world number two Scottie Scheffler.

But Scheffler would crack in the miserable conditions, taking four bogeys on his first nine, including two to start his day, on the way to a three-over 73 that put the American four back alongside Briton Justin Rose (69).

Koepka heads into Sunday in a familiar spot.

He also had the lead going into the Masters final round at Augusta National last month before a collapse opened the door for Jon Rahm to grab the Green Jacket, denying LIV Golf major recognition.

"To just never think the way I thought going into the final round," said Koepka about lessons learned from the Masters. "Learning what I learned at Augusta kind of helped today.

"I won't do it again the rest of my career.

"But that doesn't mean that you can't go play bad - you can play good, you'll play bad but I'll never have that mindset or that won't ever be the reason."

Critics of LIV Golf have branded the Saudi-bankrolled big-money venture as uncompetitive and little more than a sportwashing enterprise by a country eager to polish its human rights record.

A Koepka victory would not end the human rights questions but would give the rebel circuit some of the credibility and legitimacy it is fighting for.

LIV Golf will offer a double-barrel threat on Sunday with Bryson DeChambeau lurking just three back after returning a 70.

A battling Rory McIlroy remains on the edge of contention at one-under.

The world number three, as he has all week, continued to grind away, carding a one-under 69 to stay in the hunt.

From the first players off at 8:10 am until the last pairing of Scheffler and Conners almost seven hours later, the East Course had been pounded by often torrential rain that dumped more than half-inch (12 millimetres) on the already challenging layout.

The downpour did not deter spectators, but the large crowd appeared to be in an ugly mood by the time Koepka and DeChambeau teed off in the third last grouping, loudly jeering the LIV Golf standard bearers.

Once bitter rivals, the pair are now team mates united in LIV Golf's feud with the PGA Tour and took the boos in stride.

"I think we have a common goal - growth of the game," said DeChambeau about his relationship with Koepka. "It's New York, and I expect it (boos) here.

"I appreciate the fans, them doing that to me. I've got no problem, either way."