Defending champion Brooks Koepka has no doubts that he will convert his commanding lead into a fourth major title in his last eight starts in the US PGA Championship at Bethpage.

A third round of 70 left Koepka on 12 under par and seven shots ahead of world number one Dustin Johnson, Harold Varner, Luke List and Thailand’s Jazz Janewattananond, with England’s Matt Wallace and Japan’s Hideki Matsuyama a shot further back.

Greg Norman famously lost a six-shot lead in the final round of the 1996 Masters, but asked if he had any doubts about completing a wire-to-wire victory on Sunday, Koepka said: “No. I feel confident. I feel good. I feel excited.

“I don’t know what the (weather) forecast is but if I can hit a few fairways, there’s really a couple of key holes out here. If you play seven well, play 10 and 12 well, then from there you just hit the centre of the greens and try to par this place to death.

“I’m definitely not going to let up, I promise you that. I’d love to force it on the field and make it where it’s as big as a lead as I possibly can get. It would be nice to be able to make a 10 on the last hole and be okay.

“But I’m just playing to play good golf and wherever that puts me, I’ll be satisfied if I just go play one more good round.

“If you start treating tomorrow’s round differently than every other round, I feel like that’s where I would maybe be nervous.

“It’s just like any other round I’ve ever played. It’s 18 holes. Try to hit the fairway. Try to hit the green and try to make birdie.”