(CNN) -- Rory McIlroy held his nerve to maintain the lead on day three of the PGA Championship at the Valhalla Golf Club in Kentucky and will take a slender one shot cushion into Sunday's final round.
The Northern Irishman, who is attempting to win his third straight tournament and second major of 2014, carded a round of 67 Saturday to leave him on 13-under-par for the week.
Austria's Bernd Wiesberger is a shot back at 12-under-par followed by Rickie Fowler on 11-under.
Phil Mickelson finished the day at 10-under-par alongside Jason Day while Louis Oosthuizen, Henrik Stenson, Ryan Palmer and Miko Ilonen are tied for fifth position at nine-under-par.
"I'm really happy with how I finished again," McIlroy told Sky Sports upon reaching the clubhouse. "I finished really strongly which puts me in good position for tomorrow."
McIlroy won the British Open in July and reclaimed the world No. 1 spot last week when he picked up the WGC Bridgestone Invitational title.
And his big-hitting game seemed made for the tender greens in Louisville that had been softened by early morning rain.
But the day was not without its challenges and McIlroy had to dig deep to fend off the chasing field.
The 25-year-old saved par on the fourth after teeing off into the hazard before carding birdies on holes five and seven.
He bogeyed eight and then once again showed guile to par the ninth when he overshot the green. A birdie on ten was then followed by a bogey on 12 and another difficult par save on 13.
At this stage Day, Fowler and Palmer had clawed McIlroy back to tie for the lead at 10-under-par.
But the Rory McIlroy of the last month has been nothing if not resilient.
He spoke Friday about how golf has become his life since splitting from fiance Caroline Wozniacki in May. And when the pressure was on here in Kentucky, he excelled.
A birdie on 15 was followed by a miraculous approach shot on 16 that dropped two feet from the hole.
Three birdies from Wiesberger on the final three holes, however, brought the Austrian level atop the leaderboard.
But McIlroy added one last birdie of his own on 18 to secure the overnight lead.
"I knew there were guys ahead of me making birdies and it gives me a lot of confidence knowing that if I get challenged and people put the pressure on I am able to respond like I did today," McIlroy said.
"If I can keep playing well and staying mentally strong, there is another major to maybe come my way."
By comparison, Wiesberger will be aiming for his first ever major win when he heads out Sunday.
The 28-year-old is ranked 70 in the world and had only ever made the cut once in five previous majors.
"I played beautifully today, I didn't miss a lot of shots, set up a few nice opportunities on the last few holes especially. I'm very proud of myself the way I played," Wiesberger said in quotes carried by UK news agency, the Press Association.
"It's a completely new situation for me, only my second cut in a major in six attempts, so I am quite a rookie in this particularly situation. I have driven it really nicely this week and if I can do it again it will settle down the nerves and I am going to have fun tomorrow."
Elsewhere on the course, former world No. 1 Adam Scott scored a fine 66 to leave him tied at seven-under par with Lee Westwood, Hunter Mahan, Kevin Chappell and Jim Furyk.
Wales' Jamie Donaldson is a shot ahead at 8-under-par after scoring an impressive 66 alongside Graham DeLaet and Steve Stricker.
At the other end of the leaderboard, Bubba Watson's frustrating form continued as he scored a disappointing round of 73 leaving him two-over-par for the tournament.