Born-again Brooks Koepka is poised to strike a major blow for LIV Golf after seizing control of the weather-hit 87th Masters at Augusta National.

The former world No.1 followed up his opening round of 65 with a bogey-free 67 on Friday to surge to 12 under par and a four-shot clubhouse lead as lightning forced officials to call an early end to Friday's second round.

Fans were evacuated and a towering pine tree fell amid dark clouds and dramatic scenes but it was all looking rosy for Koepka as the four-time major winner continued his form resurgence with three more birdies and an eagle three on the par-5 eighth the highlights of his bogey-free round.

In all, he played the four par-5s in five under.

"It was really solid. Didn't really do too much wrong," Koepka said.

"Maybe the speed kind of got me on a few putts. Wasn't hitting them hard enough there towards the end, but I was striking the ball really well and leaving it in good spots.

"And that's what you've got to do. You've got to make birdies on these par-5s, take advantage of them. And I did a good job of that."

The winner of last week's LIV Golf International, Koepka was among 18 players from Greg Norman's Saudi-backed breakaway league to tee up at the year's first major.

The doubters predicted golf's outcasts - including Australia's reigning British Open champion Cameron Smith - would lack the competitive edge to compete with the PGA Tour stars after playing only a light schedule in 2023.

But while Smith and others have been struggling to keep up during the opening two rounds, Koepka has set a cracking pace.

His closest pursuer through two completed rounds is US amateur Sam Bennett, whose successive 68s playing alongside world No.1 and defending champion Scottie Scheffler left the upstart four strokes behind Koepka at eight under.

Of the chasers on the course, Jon Rahm, two under through nine holes before play was stopped for a second time, was three back at nine under.

But Koepka sounded a warning to his challengers, saying he finally felt "not far off" his brilliant best from 2017 to 2019 when he won a pair of US Open and US PGA Championships before needing knee surgery and subsequently battling self doubts.

"I've got a completely different knee, so the normal is a little bit different," the former world No.1 said.

"But swing-wise, it still feels the same. I'm able to do everything I need to. And the confidence is there. The confidence was lost just because of my knee and that was it."

Collin Morikawa signed for a second straight 69 to be six under, with Australian Jason Day (67-72) one further back at seven shots off the pace.

Day had been only one behind but dropped four shots over his last four holes in a depressing finish to an otherwise fine second round featuring five birdies.

Sam Burns (71) and former champion Jordan Spieth (70) were tied for sixth with Day.

Upstaged by his amateur playing partner, Scheffler's second-round 75 left him 11 shots adrift of Koepka at one under.

At least Scheffler will make the cut.

Some of golf's biggest names, though, won't play on the weekend.

Rory McIlroy's ninth quest to complete a fabled career grand slam is almost certainly over after a second-round 77 left the world No.2 at five over and two shots outside the projected cut line.

LIV's former Masters champions Sergio Garcia and Bubba Watson, six and seven over respectively during the stoppage, are also well outside the cut mark.