MEXICO CITY — Justin Thomas fired a six-under par 65 to seize a one-stroke lead over fellow American Patrick Reed and South Africa's Erik van Rooyen after Saturday's third round of the WGC Mexico Championship.

World No. 4 Thomas, the 2017 PGA Championship winner, opened and closed with bogeys but made eight birdies in between to stand on 15-under 198 after 54 holes at Chapultepec Golf Club.

"I would have liked to have birdied the first hole to have seen what would have happened — I hit four bad shots on that hole," Thomas said.

"I've gotten better just in general. I feel like I'm playing well enough where if I don't play them all well I can play four or five in a row and get pretty hot."

Thomas has managed three top-10 finishes at the Mexico event, including a runner-up effort to Phil Mickelson in 2018, but he yearns to finally capture the trophy.

"I really want that first place," Thomas said. "I've been close a couple times. I definitely feel like I have a little bit of unfinished business here.

"I know I have to play well tomorrow but I want it."

Reed, the 2018 Masters champion, closed with a bogey to settle for a share of second with van Rooyen after both shot 67 to finish on 199.

Spain's Jon Rahm shot a course-record 10-under 61, with a one-bounce ace at the par-3 17th, to share fourth on 202 with world No. 1 Rory McIlroy of Northern Ireland and American Bryson DeChambeau.

England's Paul Casey and Tyrrell Hatton shared seventh on 203.

Thomas opened with a bogey, going well right of the cart path off the tee, but answered with birdies on the next two holes, sinking a 16-foot putt at the par-3 third, and made another from seven feet at the par-5 sixth.

He began the back nine with back-to-back birdies, made two more at the 14th and par-5 15th then dropped his approach just inside 14 feet at the par-3 17th and made the birdie putt.

Another bogey at 18, where Thomas missed a par putt from six feet, opened the door for Reed, but he couldn't charge through.

Reed had back-to-back birdies to start the back nine and again at 14 and 15 but he found the right rough off the 18th tee and a greenside bunker, then blasted out to the fringe and came up short on a 17-foot par putt.

Rahm birdied six of the first seven holes before making a three-putt bogey from 45 feet at the par-4 eighth. He birdied the par-4 10th, par-3 13th and 15 before holing out from the 17th tee.

"I think a lot of us like to talk sometimes about how unlucky we get — today I got fortunate," Rahm said. "I hit the right shots and I got the right bounces and I took advantage of it."

He said he knew it could be a special day when he had four birdies to open his round.

"When I basically had tap-in, tap-in, tap-in, and 10 feet for a birdie," said Rahm, who said his goal was "to get as close as possible to the leaders." — AFP