San Francisco - Jordan Spieth fired eight birdies in a seven-under par 65 on Saturday to seize a six-shot lead after three rounds of the weather-disrupted US PGA Tour Pebble Beach National Pro-Am.
Spieth, in a three-way tie for the lead with world number one Jason Day and Derek Fathauer when the second round concluded early Saturday, pulled inexorably away with a sparkling effort at Pebble Beach Golf Links, one of three courses in use over the first three rounds of the tournament.
The two-time major champion, seeking his first PGA title of 2017, opened with back to back birdies. His only bogey of the round, at the eighth, was followed by three birdies in a row at the ninth, 10th and 11th.
Having picked up another shot at 15, he rolled in a 16-footer for birdie at the par-three 17th, and left himself inches for a birdie at 18.
"I couldn't have asked for a better putting day, with greens that are poa annua and have a lot of traffic because they have been so soft with this weather, it's very difficult even to make a putt from four feet," said Spieth, whose 17-under par total of 198 put him six in front of American Brandt Snedeker, who carded a five-under 67 at Pebble Beach.
It was a further stroke back to two-time winner Dustin Johnson and unheralded Kelly Kraft, Americans who posted 65s for 205.
World number one Day made a disastrous start to the third round with three bogeys and a double bogey in his first six holes at Pebble Beach.
He finished on a stronger note with three of his five birdies in his last four holes -- but not before his card was marred by another double bogey at his 14th hole of the day, Pebble's par-three fifth.
Day signed for a three-over 75 that left him 10 off the pace.
"It was kind of a tough one for me out there," Day said. "It was just a mistake after mistake on the front side for me and unfortunately, that's sometimes how it goes. To be honest, I just kept on making silly errors and mistakes out there.
"But, you know what, I think with how I played on the back side, I feel good about going into tomorrow and trying to build momentum for next week's tournament."
Spieth said his most satisfying putt of the day wasn't even for birdie, but to save par at the 12th.
"I knew what the putt was doing, but it's one of those kind of left-to-right that you've got to go outside the hole and you don't really want to ... and I trusted the line and it went right in the dead center."
Despite Spieth's big cushion, Snedeker -- a two-time winner at Pebble Beach -- thought he could put challenge him on Sunday.
"The front nine will be huge tomorrow, the first seven holes, I've got to go out there and make some birdies and put some pressure on him," he said. "If you don't get the first seven holes at Pebble, you're going to have a long day, so I know what I have to do."