Spieth storms five clear at Tournament of Champions

That gave Spieth a superb eight-under-par 65 and a 24-under total of 195 after 54 holes at the Kapalua Resort, despite not being at his pinpoint best with his iron play for much of a blustery day on the Hawaiian island of Maui.

"I just tried to put a smooth swing on it," Spieth, 22, told Golf Channel about his three-iron approach at the last. "It came across the hole and took a peek, I guess (at dropping in).

"It was really nice to get that putt to go in. I think I deserved it on this hole and it gives me a nice little confidence boost into tomorrow."

Fellow American Brooks Koepka was alone in second after shooting a best-of-the-week 63, with defending champion Patrick Reed a further stroke back at 18 under par after pocketing four birdies in the last five holes for a 67.

Spieth, who would match Tiger Woods with a seventh PGA win before the age of 23 should he triumph on Sunday, was delighted to rebound from a poor stretch of holes from the short eighth, which he bogeyed after missing the green.

"I'm extremely pleased, especially the way we bounced back after that stretch eight through 11," the Masters and U.S. Open champion said after a round that also included seven birdies.

"It started to look like I was slapping it around a bit. I just needed one thing to go my way there and I got that long putt on 12 (from 50 feet), then all of a sudden we turned things around on the easy holes."

Spieth is also on track to beat the tournament record of 31-under set by Ernie Els in 2003 but he is wary of the final-round challenge posed by compatriots Koepka and Reed, who have both displayed brilliant golf at Kapalua this week.

"Brooks shot 10 under today, and that's insane," said Spieth. "I'm going to have to go out and make some birdies. I've got to expect Brooks and Patrick to shoot eight or nine under tomorrow."

(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Larry Fine/Steve Keating)