Atlanta - World No 1 Rory McIlroy fired a three-under par 67 on Saturday to match Billy Horschel for the lead entering the final round of the US PGA's season-ending Tour Championship.
Northern Ireland's McIlroy, this year's British Open champion and PGA Championship winner, and American Horschel, who shot a third-round 69 for his 11th sub-70 round in a row, stood level on nine-under par after 54 holes at East Lake.
A showdown was set not only for the $1.4m top prize for winning the tournament but also for the $10 million FedEx Cup season points playoff bonus.
McIlroy and Horschel are among the five points leaders who will capture the rich bonus prize simply by winning the tournament. Anyone in the field of 29 can take the bonus but most would need to win and have a major collapse by the co-leaders.
McIlroy, a combined 81-under par since he took the Claret Jug in July, fired Friday's low round of 65 and battled through hot and humid Saturday conditions to grab a share of the lead.
"When you look at the score, 67 is a good score in the circumstances," McIlroy said. "But it really wasn't much to look at out there.
"I haven't played my best golf out there this week. I've just been able to grind it out. If you're not playing well, you still find a way to hole your putts and find a way to grind out scores like I've been doing this week."
McIlroy sandwiched birdies at the first and third holes around a bogey at the second to begin the round.
He two-putted from 55 feet to birdie the par-5 fifth, but missed a 3-foot par putt at 10 to stumble back.
McIlroy's biggest shot came at the par-5 15th when he put his second shot 27 feet from the hole and curled in the eagle putt to grab a share of the lead.
Horschel, McIlroy's playing partner in the final duo, birdied the par-3 second and closed the front nine with back-to-back birdies but stumbled with bogeys at 10 and 13, opening the door for McIlroy.
"I was holding onto the reins pretty tight," Horschel said. "I wasn't putting the ball in the fairway. When you do that on the back nine it challenges you.
"But I was able to hold it together and get a respectable number I can be happy about."
Horschel, whose wife is expecting a baby later this month, led after 54 holes on his way to winning last week in Denver.
A victory Sunday would bring Horschel more money in one day, $11.4 million, than he has earned in his entire career so far. That had Horschel nervous and wishing he could start the fourth round just after the third had ended.
"You like to feel nerves," Horschel said. "It makes you feel alive. I really am loving it."
Jim Furyk put his approaches within four feet at the 12th and 13th holes to set up birdie putts and followed with a 38-foot birdie putt at the 16th on his way to a 67 to stand third on 203.
"I felt really good about it," Furyk said. "I had a lot of opportunities on the back nine, made a lot of putts, hit it really close on 12 and 13 and had a really good nine holes."
England's Justin Rose, Australian Jason Day and American Rickie Fowler shared fourth on 204 with Americans Russell Henley, Chris Kirk and Ryan Palmer on 205 and Aussie Adam Scott on 206.
Among them, only Kirk could claim the bonus just by winning.
Scores after Saturday's third round of the US PGA Tour Championship (par 70, USA unless noted):
201 - Billy Horschel 66-66-69, Rory McIlroy (NIR) 69-65-67
203 - Jim Furyk 67-69-67
204 - Rickie Fowler 69-68-67, Justin Rose (GBR) 72-66-66, Jason Day (AUS) 67-67-70
205 - Russell Henley 70-68-67, Ryan Palmer 69-67-69, Chris Kirk 66-68-71
206 - Adam Scott (AUS) 69-72-65
207 - Bubba Watson 67-73-67
208 - Matt Kuchar 68-71-69
209 - Gary Woodland 71-75-63
210 - Sergio Garcia (ESP) 69-71-70, Cameron Tringale 68-68-74
211 - Jimmy Walker 73-69-69, Kevin Na 70-66-75
212 - Bill Haas 68-71-73
213 - Hideki Matsuyama (JPN) 71-71-71
214 - Zach Johnson 68-74-72
215 - Martin Kaymer (GER) 73-69-73, Patrick Reed 67-74-74
216 - John Senden (AUS) 72-75-69, Morgan Hoffmann 70-73-73
217 - Hunter Mahan 74-72-71, Brendon Todd 70-75-72
218 - Webb Simpson 74-72-72
221 - Jordan Spieth 71-70-80
227 - Geoff Ogilvy (AUS) 77-77-73