Keegan Bradley, trying to win the Byron Nelson Championship for the second time in three years, fired a two-under 68 to cling to a one-stroke lead over South Korea's Bae Sang-Moon.
In windy conditions at the par-70 TPC Four Seasons Resort course, Bradley closed with a bogey for the third round in a row but the American still stood atop the leaderboard on 13-under 197 with Bae on 198.
Nathan Green was the best-placed Australian, firing a two-under 68 to head into the final round six shots off the pace.
Fellow Australians Marc Leishman and Cameron Percy were two shots further back on 205.
Jason Day fired five birdies on his way to an impressive four-under 66 to surge 49 places up the leaderboard and finish the round on 206. Stuart Appleby was one stroke behind on 207.
Bradley was elated to have maintained his lead.
"I'm playing really well," he said. "I'm proud of how I played the last two days and I'm happy with where I'm sitting."
Bradley won his first US PGA title at the 2011 Byron Nelson and went on to win the 2011 PGA Championship in his first major appearance.
He could become first wire-to-wire winner at the Byron Nelson since 1980, when Tom Watson won the event for a record fourth time by capturing his third Byron Nelson in a row. Mark Hayes also did it in 1976.
American Tom Gillis was third on 199 after concluding his round of 67 with a 13m birdie chip-in from a greenside bunker, with compatriot Scott Piercy fourth on 200 after a 66 that featured several long birdie putts.
South Africa's Charl Schwartzel, the 2011 Masters champion, was in a group sharing fifth on 202 that included Americans Harris English, John Huh and Gary Woodland. Australian Nathan Green was alone in ninth on 203.
Bae, who has won 11 times worldwide but has never won a US PGA event, began with back-to-back birdies before taking his lone bogey at the par-3 fifth. He added birdies at the par-4 eighth, par-3 13th and 16th to keep the pressure on Bradley.
197: Keegan Bradley (USA) 60 69 68
198: Bae Sang-Moon (KOR) 66 66 66
199: Tom Gillis (USA) 69 63 67
200: Scott Piercy (USA) 66 68 66.