Steve Flesch birdied four of the last five holes on Saturday to stretch his lead to four strokes heading into the final round of the Turning Point Resort Championship in Verona.

The left-handed American, who led by one after 36 holes, fired a six-under-par 66 for a 19-under-par 197 total, four strokes better than Sweden's Carl Pettersson and compatriot Charles Warren on the 7,482-yard Atunyote Golf Club course.

Pettersson posted a six-under 66 and Warren registered a 68 to complete 54 holes at 15-under-par.

The 40-year-old Flesch, who won last month's Reno-Tahoe event, said he corrected a flaw in his swing that he noticed from a photograph in the local newspaper on Saturday.

"I was too upright," Flesch told reporters. "So I levelled out my shoulder turn a little bit today. I tried to flatten out my swing plane a little bit and I hit it pretty good."

Pettersson, aiming to notch a U.S. Tour victory for the third season in a row, said: "I'm going to have to go out and shoot low. Obviously, Steve has played phenomenal and you have to shoot a low number tomorrow and see what happens."

Alone in fourth place was another American, Parker McLachlin, whose 65 was the day's lowest round and put him at 203, six strokes off the pace in the first of seven tournaments that comprise the U.S. Tour's fall series.