Defending champion Brooks Koepka plays a tee shot during Saturday's third round of the PGA Championship

Bethpage (United States) (AFP) - Defending champion and runaway leader Brooks Koepka made a frustrating bogey to close the front nine but still owned a seven-stroke lead at the turn in Saturday’s third round of the PGA Championship.

Third-ranked Koepka, in prime position for his fourth major title, made the turn at Bethpage Black on 13-under par after two birdies and an around-the-edge miss on a tap-in par putt at the ninth hole.

The 29-year-old American owned an seven-stroke lead over world number one Dustin Johnson and Thailand’s Jazz Janewattananond, his only rivals within nine shots.

No one in major golf history fired a lower 36-hole score than Koepka’s 12-under 128, and his seven-stroke lead was the second-largest halfway edge, trailing only Henry Cotton’s nine-shot advantage in the 1934 British Open.

If Koepka does capture the Wanamaker Trophy and the $1.98 million (1.77 million euros) top prize, he will be the first man to own back-to-back titles at two majors simultaneously. Koepka seeks a third consecutive US Open crown next month at Pebble Beach.

“He’s definitely, in these events, playing on a different level than most anyone else,” four-time major winner Rory McIlroy said of Koepka. “It’s awesome. It’s so good. It’s great to watch.”

Kopeka’s routine tee blast and wedge approach made him a threat on holes when he found the fairway. He missed a six-foot birdie putt at the first but sank a five-footer at the second and a three-footer at the fifth to reach 14-under and lead by eight.

Koepka found tall weeds and greenside rough at the seventh but rescued par by sinking a nine-foot putt and saved par again after missing the green at the par-3 eighth, only to botch his last par putt before starting the back nine.

The PGA’s largest-ever 54-hole lead was five strokes, last achieved by Ray Floyd in 1982, and the low 54-hole tournament score was 196 by David Toms in 2001.

Koepka already owns the PGA 18-, 36- and 72-hole scoring records.

American Jordan Spieth, seeking a win to complete a career Grand Slam, and Australian Adam Scott were Koepka’s nearest rivals when the day began.

Spieth, a winner at the 2015 Masters and US Open plus the 2017 British Open, found a greenside bunker to bogey the fifth and took double bogey at the ninth to fall back.

Scott, seeking his second major title after the 2013 Masters, missed the green to bogey the par-3 third. He sank a three-footer to birdie the par-5 fourth before bogeys at seven and nine dropped him back.

- Rose, Jazz sparkle -

Second-ranked Justin Rose, the 2013 US Open champion, and Matt Wallace were each bidding to become the first Englishman to win the PGA since Jim Barnes in 1919.

Rose sank a 50-foot birdie putt at the 12th to stand level for the day and 3-under overall, one shot behind Wallace, also level on the day.

Johnson is trying to keep Koepka from overtaking him atop the rankings as well as seeking a second major title after the 2016 US Open.

Johnson birdied three of the first four holes to gain ground, but another birdie at nine was offset by a bogey at 10.

Thailand’s 72nd-ranked Jazz sizzled early with three birdies in the first six holes, putts from seven feet at the third, twice as far at the fourth and four feet at the sixth.

The 23-year-old from Bangkok, playing in his first PGA Championship, also curled in a tricky 13-foot birdie putt at 10.