American Davis Thompson carded a nine-under 62 to hold a two-shot lead going into the final round of the John Deere Classic in Illinois.
Thompson hit nine birdies in his third round to top the leaderboard on 21 under ahead of England’s Aaron Rai and compatriot Eric Cole.
Rai, who shared a one-shot lead with Chinese Taipei’s CT Pan going into the third round, shot a five-under 66 featuring six birdies.
Pan is two shots further back alongside American Hayden Springer.
It is the first time Thompson has led going into the final round of a PGA Tour event, as he seeks a first victory.
“I guess it was just my day today,” said Thompson. “The guys behind me are playing really well.
“I know it’s going to be tough to finish off a golf tournament, but I’ve done it before. I just have to stay present-minded.”
England’s Harry Hall began the day one shot off the lead but slipped down the leaderboard after carding a one-under 70.
Two-time winner Jordan Spieth shot an eight-under 63, the second-best score of the day, to sit in a tie for 12th place at 14 under.
The final day will be played in threesomes with a delayed start in an attempt to beat forecast storms, meaning Rai will be in the final group with Thompson and Cole.