An and Im both played flawless rounds to move one shot clear atop the leaderboard after a low-scoring first round at Sedgefield Country Club in Greensboro, North Carolina.

An reeled off eight birdies and 10 pars in a bogey-free start to his latest attempt to win a maiden PGA Tour title.

The 27-year-old from Seoul has twice lost in playoffs on the PGA Tour, being beaten in the 2016 Zurich Classic before losing out to Bryson DeChambeau in a three-way playoff at Memorial last year.

On Thursday, An's short game worked beautifully, helping him carve out a series of birdie chances which he duly converted.

A solid start saw him reach the turn at four under, before a hat-trick of birdies on the 13th, 14th and 15th holes vaulted him up the leaderboard. The highlight came on the par-four 14th, when he holed out from 37 feet for birdie.

A further birdie on the 17th took him to eight under.

"Four under on the front, four under on the back, it was definitely a good finish," An said. "It was pretty solid all day."

The 21-year-old Im, meanwhile, who is also chasing a first PGA Tour win after two victories in 2018 on the Web.com Tour, matched An virtually shot-for-shot with his 62, which also comprised eight birdies and 10 pars.

Im, who started on the back nine, birdied two of his final three holes to grab a share of the lead.

Im and An are one shot clear of four players tied for third on 63 -- Canada's Mackenzie Hughes, South African-born Slovakian Rory Sabbatini and Patrick Rodgers and Johnson Wagner, both of the United States.

Former world number one Jordan Spieth and Brandt Snedeker are lurking in a cluster of nine players on 64, two off the lead.

Spieth's round included six birdies and an eagle, and the American would have had a share of the lead had it not been for bogeys on the 12th and 18th holes.

The highlight of Spieth's round was his eagle at the par-five 15th. A superb approach shot got him onto the green in two, and he then buried a 19-foot par for a three.

Another scintillating approach shot set him up for a birdie on the 17th, drilling an iron from 148 yards to three feet for a tap-in.

Eleven players, including England's Paul Casey and Scotland's Martin Laird, are a further shot back.