FARMINGDALE, N.Y. -- Brooks Koepka's mastering of the majors continued Thursday at Bethpage Black, where he scorched the harsh layout in the first round of the PGA Championship with a course-record 63.

Koepka, who also shot 63 on his way to victory at the PGA last summer in St. Louis, did not make a bogey and had seven birdies to tie a tournament record for lowest score. He leads by one over Danny Lee, who had a 64 during the afternoon wave, and is four ahead of Tommy Fleetwood.

"I've never been this confident,'' said Koepka, 29, who has won three major championships in the past two years and came up a shot short against Tiger Woods last month at the Masters. "I think I'm still learning, understandably, my game, and I've figured it out. I think over the next few years, I'm excited for what's to come.

"I understand a lot more about my misses, where to hit it, and major championships I just suck it up. You don't always have to aim at the flag like you do in regular events. Sometimes it's just about how few bogeys and doubles you make this week."

Koepka didn't have any of those Thursday, even though he had some wayward tee shots to overcome. He managed to do so by hitting 14 of 18 greens and holing a couple of ticklish par putts; he needed just 25 putts for the round.

He now has gone 31 straight holes without a bogey in the PGA Championship, and this was his 10th straight round under par in majors. His 63 was the 17th in PGA Championship history, and he is the first player to post a 63 in consecutive years at major championships.

In addition, he is just the third golfer with multiple rounds of 63 in major championship history, joining Greg Norman and Vijay Singh.

Ranked fourth in the world, Koepka figured to be a good match for Bethpage Black, a difficult test even in benign conditions. Cool temperatures and an abundance of rain this week made it play even longer than the 7,459 yards.

"That was one of the best rounds I've played probably as a professional," Koepka said. "This golf course is brutal. If you're not going to drive it, it tests every aspect of your game. You've got to drive the ball straight. It's long, so you've got to hit it far and really position yourself with some of these shots in.

"You can't take a shot off, and that's what I love. I think that's why I play so well at U.S. Opens -- this golf course is a typical U.S. Open golf course. If you don't have a good day, you can very easily shoot 5, 6 over. There's a fine line between 5, 6 over and a couple under out here."

Woods was the only player at 3 under to finish under par at Bethpage during the 2002 U.S. Open. Lucas Glover was 4 under when he won here in 2009.

And it was Woods who said Thursday that the 63 by Koepka "was the worst he could have shot. He played well. He had a couple of putts he didn't make."

Said Koepka: "I didn't take care of the par-5s, didn't birdie any of the par-5s. That was disappointing because I felt like, you know, those are holes you should be able to birdie. Definitely can reach 4, and [I] hit a bad driver there. And 13, I can get there, too, and [I] hit it in the bunker. And then the second hole today, my 11th hole, I missed about a 5-footer. That would have been nice to shoot 60. I guess that would have been pretty good."