LOS ANGELES (AFP) — Wyndham Clark surged into a commanding five-stroke lead at the BMW Championship on Saturday, bouncing back from an opening-hole double bogey to fire a superb round of 65.

Having started moving day just one stroke clear, Clark left the field in his wake with six birdies, and an eagle on eight, at Bellerive Country Club in St. Louis, Missouri.

The double US Open winner will enter the final day of the penultimate event of the PGA Tour's FedEx Cup playoffs on 17-under, joined in the final pair by Rory McIlroy on 12-under.

"Overall, awesome day," Clark said.

Clark's hot streak to score Saturday's joint best round was all the more remarkable given how his day began.

After a bogey-free first two days, the overnight leader botched an ambitious shot from the lip of a fairway bunker and badly misjudged the green for a double-bogey on one.

"It was an unfortunate break... probably should have just chipped out and played for bogey," he said.

Clark quickly regained the joint lead with Gary Woodland, his birdie putt just wobbling in on four, before a superb wedge from deep rough for birdie on seven.

An eagle on eight from a pinpoint iron and 12-foot putt gave Clark a three-stroke cushion.

And the American soared clear on the back nine, with birdies at 10 — thanks to a 30-foot putt — 11, 13 and 14.

He saved par with a 15-foot putt on 16 but missed a simple five-foot birdie putt on 17 and then another par putt on the last to give the field hope.

"Got into a great groove and played amazing. I'm just a little bummed right now at how I finished on 17, 18," he said.

With Woodland struggling, McIlroy surged into joint second. The Northern Irishman carded an entertaining 65, despite finding just four fairways all day.

He had birdied the par-three third and escaped a wayward drive on eighth with a par after somehow bulldozing his second shot straight through both a tree and a bunker.

Pushing the accelerator, the six-time Major champ's game sprang to life on the back nine, with five birdies — including a 26-foot putt on 16 — closing the gap to Clark.

"Playing this golf course from the rough isn't fun. But I hung in there. My short game saved me a couple of times," McIlroy said.

"I'm in a good spot going into tomorrow in terms of where I'm at at the leaderboard. But it's going to take a heroic effort from one of us to catch Wyndham."

He added: "I think you can be aggressive here."