(REUTERS) - Rookie Austin Cook edged closer to his maiden PGA Tour title after firing a third-round four-under par 66 for a three-stroke lead at the RSM Classic in Sea Island, Georgia, on Saturday (Nov 18).

The 26-year-old collected his first bogey of the week but picked up five birdies at the Seaside course to reach 18-under 194, with former winner Chris Kirk (64) his closest challenger on 15-under.

Brian Gay, who turned in a 69, is alone in third place another stroke back while J.J. Spaun had eight birdies in a round of 62 to leave him in fourth place at 13-under 199.

Overnight leader Cook got off to a great start with birdies at the first two holes before making a clutch par at the third.

"We got a few putts to go early and just kind of kept the course," he told PGA radio. "It could have gotten ugly pretty quick if I didn't get the ball quite up that hill," Cook said after a poor tee shot on three.

"But we were able to hit it to about eight feet and make the putt and keep the momentum."

Two more birdies, at the seventh and ninth, took him to the turn at 4-under but he stumbled at 14 with a three-putt bogey.

Cook did not allow his first dropped stroke of the week to get to him, however, as he hit back right away with another birdie.

"I've grown a lot maturity wise, mentally," Cook said. "Nowadays, I'm trying to work really hard to let things slide off my shoulder."

Kirk, who won the tournament in 2013, kept the pressure on with seven birdies and a bogey. "It's nice to be back in contention," he said.