Fowlers was the first to break the record when he carded an eight-under-par 62 before Schauffele matched that feat 20 minutes later.

South African Branden Grace is the only other golfer to break 63 in the four men's majors having posted a third-round score of 62 in the third round of The Open Championship in 2017.

After failing to qualify for the past two U.S. Opens, Fowler marked his return in sensational fashion, tying the tournament record of 10 birdies in his round that also featured two bogeys.

"It has been long and tough, it’s a lot longer than you ever want it to be," said Fowler on his resurgence in form.

"It’s been so worth it and now being back."

Schauffele, who has finished in the top three in three of the four majors but has yet to be crowned champion, scored eight birdies in a bogey-free round.

"It’s a great start," said the Tokyo 2020 Olympic gold medallist.

"I hit a lot of really good shots.

"Rickie was just right in front of me and I was playing really good golf so thought I may as well just chase him down.

"You have to play hard here, dig your around."

The top five is dominated by Americans with Wyndham Clark and Dustin Johnson tied third on six under and Brian Harman level with Northern Ireland’s Rory McIlroy on five under.

Four-time major winner McIlroy has notoriously struggled to make strong starts in the majors but got off to a flier in LA, making five birdies on the front nine before adding another on the 15th hole.

Johnson, the 2016 U.S. Open champion, landed seven birdies and one bogey in a fine round of 64.

"The golf course is in perfect condition," said Johnson.

"I really like it.

"You just have to drive it well or you have no chance.

"The course was set up really nicely.

"I would imagine the next few days you’re going to see the golf course set up as hard as they want to."