South Korea's An Byeong-hun had four birdies in firing a four-under-par 66 on Saturday to maintain his one-shot lead heading into the final round of the US PGA Tour Wyndham Championship.

An, chasing a first US PGA Tour title, notched his third straight bogey-free round on the par-70 Sedgefield Country Club course in Greensboro, North Carolina.

The 27-year-old from Seoul was pleased with that, but said it might not be enough to deliver his trophy breakthrough. 

"I'm still only one ahead. You never know what's going to happen," he said. "You can make a lot of birdies out here, so I definitely need to keep my foot on the pedal."

Americans Webb Simpson and Brice Garnett shared second on 194, Simpson posting a five-under 65 that included six birdies and a bogey and Garnett a 66 that featured six birdies and two bogeys.

American Ryan Armour fired a 65 and was alone in fourth on 195.

An, who has a European Tour title on his resume and three runner-up finishes on the US Tour, said scrambling was the key to his third round - particularly a par save after an errant drive at 15.

"That up and down was huge," said An, who had just rolled in a 51-foot birdie putt at the 14th when his driver off the tee at 15 sailed right.

"It's nice to hold the lead," said An, who added his plan for Sunday was to "try to make as many birdies as I can and not make any silly mistakes."

Simpson is in contention in the tournament where he claimed his first title in 2011 and finished second last year.

The North Carolina native is seeking a sixth US tour title and his first since the 2018 Players Championship. He was second last week at the WGC-St. Jude Invitational in Memphis.

"I had a chance to win there," Simpson said. "I played well down the stretch. It's one of those feelings that you're happy you played well and you had a hot finish at a good tournament, but you're first out of winning.

"So it did create some more hunger to get back to the winner's circle."

It was a tough day for three-time major winner Jordan Spieth, who went into the round four off the lead and ended up failing to make the 54-hole cut after a seven-over 77.