Defending champion Brooks Koepka led entering the back nine in Sunday's final round of the PGA Championship

Bethpage (United States) (AFP) - Defending champion Brooks Koepka carried a four-stroke lead onto the back nine at Bethpage Black in Sunday’s windy final round of the PGA Championship, looking to complete a wire-to-wire triumph and win his fourth major title.

Koepka made the turn on 12-under with top-ranked Dustin Johnson at 8-under through 10 holes, the only rival within seven strokes.

Johnson went three-under par on the front nine in a bid to keep his top ranking and win his second major title after the 2016 US Open.

Johnson birdied the par-5 fourth and par-4 sixth and ninth holes while Koepka, who opened with a bogey but birdied the fourth, saw his lead drop as low as it has been since Friday.

A victory would restore Koepka to the world number one ranking he lost in January and make the 29-year-old American the PGA’s fifth wire-to-wire winner after Hal Sutton in 1983, Ray Floyd in 1982, Jack Nicklaus in 1971 and Bobby Nichols in 1964.

Johnson can match the top last-round comeback by a PGA winner – seven strokes by John Mahaffey in 1978.

Koepka seized a tournament-record lead of seven strokes after 54 holes on 12-under par 198. No man has led a major by so much so late and lost.

But the margin shrank quickly in breezy conditions.

Koepka stumbled at the start, twice finding the rough and missing a 12-foot par putt on the opening hole while last-group playing partner Harold Varner sank a three-foot birdie putt, trimming Koepka’s lead to five shots.

Varner fell back with double bogeys at the par-3 third and fourth but Johnson birdied the fourth to keep Koepka’s edge at five.

Koepka tapped in for birdie at four to return to 12-under but Johnson birdied the sixth from eight feet to stay five back.

Johnson hit a tree and dropped into rough at the par-3 eighth but sank a nine-foot par putt then dropped his approach at nine inches from the cup and made the birdie putt to make the turn eight-under, four behind Koepka, who closed the front side with five pars.

Koepka owns the 72-hole PGA record of 264 set last year at Bellerive when he held off Tiger Woods for the title.

Koepka would join Woods as the only back-to-back stroke-play winners of the PGA, Woods having done it in 2006-07 as well as 1999-2000.

- Koepka in good company -

Koepka would become the first player to win his first four majors in two years or less, with only Woods, Jack Nicklaus and Ben Hogan matching him for so many majors in such a span.

After a course-record 63 on Thursday, Koepka produced the lowest 36-hole score in major golf history on 12-under 128 before firing a third-round 70.

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 can also become the first golfer to defend both US Open and PGA crowns.

Koepka has only won two non-major US PGA events, the 2015 Phoenix Open for his first tour title and last October’s CJ Cup in South Korea.