Rory McIlroy took advantage of a late stumble from Dustin Johnson to surge into contention to win both the Tour Championship and overall FedEx Cup title in Atlanta.

McIlroy carded a flawless third round of 66 at East Lake to finish six under par, two behind joint leaders Johnson and fellow American Kevin Chappell.

A third win of the season on Sunday would give McIlroy the first prize of 1.5million US dollars and the four-time major winner can also pocket the 10million bonus for winning the FedEx Cup if Johnson finishes joint second or worse.

A hat-trick of birdies from the fourth had briefly taken Johnson four shots clear of the field, although the 32-year-old gave the chasing pack a glimmer of hope with a bogey on the seventh.

And worse was to come on the back nine for the US Open champion, who followed two birdies and two bogeys in a four-hole stretch from the 12th with a double bogey on the 17th.

That allowed Chappell, who had carded 11 straight pars before chipping in for birdie on the 12th, to take the outright lead with a birdie on the same hole, but Johnson recovered to birdie the 18th and get back on level terms.

McIlroy had played the front nine in a total of five over par the first two days, but followed seven straight pars with a birdie on the eighth before picking up further shots on the 13th, 16th and 18th.

“That birdie on eight was needed, I was getting a little frustrated,” McIlroy told Sky Sports. “I gave myself plenty of chances on the front nine and hit plenty of good putts that were just burning the edges. I played the back nine well this week and if you take the front nine out of it I would probably be leading the golf tournament.”

Asked about his prospects of winning the FedEx Cup for the first time in his career, the 27-year-old added: “I’m excited. First and foremost I need to go out and try to win this golf tournament. That’s what I need to focus on and if I can do that, someone has to tie with DJ for me to win.

“I’ve been close a couple of times in my career. It would be nice obviously to win, but all I can do right now is focus on myself, try and post another good number and if DJ finishes second on his own he fully deserves this FedEx Cup.

“He’s had a phenomenal year, a way better year than I’ve had, but that’s the beauty about these play-offs, you can come up from behind and give yourself a shot, which I have tomorrow.”

Johnson, who cannot overtake the injured Jason Day as world number one even with a win, said: "I hit a couple of bad drives there coming home and on this golf course if you miss the fairways it's very difficult.

“I feel like I am swinging really well but I will go hit a few balls and work on the driver a little.”

American Ryan Moore was alongside McIlroy on six under, with Japan's Hideki Matsuyama on five under and former US PGA champion Jason Dufner another shot back.

Double Masters champion Bubba Watson was nine off the lead on one over par, but nevertheless had enhanced his chances of being selected for the Ryder Cup with a 66.

Asked about trying to earn US captain Davis Love’s final wild card, the world number seven said: “The golf tournament is the only pressure because he’s been saying, and also when he talked to me a couple of weeks ago, it wasn’t about play, it was about who fits the team and pairs up nicely.

“It’s all about personality and game types, who fits up good, so whatever that means I haven’t got the call yet. So I’m waiting.”

Even if Watson is overlooked on Sunday evening, he has asked Love if he can be one of his vice-captains at Hazeltine as the home side look to avoid an unprecedented fourth straight defeat.

“I just want to be a part of it,” he added. “The experience of it, the atmosphere, everything about it is what golf is. It’s just so much fun. Even though we’re trying to beat the other team, we’re all friends at the end of it. Sunday night we all hang out, no matter who wins or loses.”