And after just 18 holes of the 146th edition of the game’s oldest championship, Americans dominate the top of the leaderboard yet again.

World No.3 Jordan Spieth, US Open Champion Brooks Koepka and Tour veteran Matt Kuchar stamped their authority on this championship with opening round five under 65s. The stars and stripes trio are one-stroke clear of England’s Paul Casey and South African Charl Schwartzel. A group of six players including Americans Justin Thomas and Charley Hoffman are a further stroke back at three under.

The rounds of the leading threesome all differed in their construction to find the same result.

Kuchar was on track to set some scoring records after he reached the turn at five under, equaling the 29 Ian Baker-Finch carded during the final round of his victory march in 1991. But the amiable 39-year-old couldn’t make a birdie on the inward nine, notching nine consecutive pars for his 65.

Brooks Koepka holes his bunker shot on 17 for eagle and a share of the lead. PHOTO: Stuart Franklin/Getty Images.

Koepka continued where he left off at Erin Hills last month and there was little sign of any rust in his game after taking a lengthy break following his victory. He had a sole birdie on the front nine but quickly raced to four under with a hat-trick of birdies starting at the 11th hole and appeared to be racing to a low number. A sloppy birdie at the difficult 16th was his only blemish in the round, but he quickly erased the error there when he holed a bunker shot on the par-5 17th for eagle.

Spieth began his round when the winds were still strong and there was moisture hanging in the air, which made his bogey-free exhibition a round to behold. Bogey-free, it might have been, but it was a long way from being flawless. While such rounds in the past have seen him rely heavily on his putting, it was his iron play from off the edges of the fairways that impressed most. He hit just five of 14 fairways during his round but still managed to hit 15 greens in regulation. When he did miss a green, his velvety soft-handed short game came to the rescue.

If he continues to put on a clinic of iron play like this during the next three days, he will add the Claret Jug to his US Open trophy and Masters green jacket.

Jordan Spieth's iron play from the rough was outstanding on day one. PHOTO: Stuart Franklin/Getty Images.

The 23-year-old even impressed himself with how well he played, putting his round in the top-five or six major rounds he has ever played.

“It could be a lot more significant in three days' time than I would consider it right now,” Spieth said. “I'd call it a top five probably, major round that I've played, maybe fifth or sixth, something like that.

“There are scores that I've shot that were closer to par that were better given what I needed to do.

“But I couldn't have done much better today. I missed two greens. I think I missed three, but one of them I was putting from the fringe. So essentially missed two greens today in some 15-mile-an-hour winds. This course has a lot of crosswinds, so it's tough to judge how far the ball is going to fly depending on what shot you play. So that speaks a lot to the ball-striking of the day.”

Spieth escapes from one of Birkdale's deep pot bunkers. PHOTO: Getty Images.

Spieth said he felt very confident heading into the first round after working hard on his putting following the US Open.

“Well, our last start was a win. I also was very close at the US Open and very close at the Masters,” he said. “The Masters, I got off to a really poor start the first day and played pretty well after that.

“But the US Open it was everything but the putter. I was in a good enough position to really do something special there the first couple of rounds of the US Open and just didn't get anything to go.

WHERE THE LEADERS STAND

“I've been putting in a lot of work with the putting and trying to get it back to the confidence that I've had the last couple of years. It's just been the one thing that's been off this year. My ball-striking has been better than in any years that I've ever played golf.”

That’s an ominous statement for the rest of the field to hear with three rounds to play.

In all, there are 39 players in red numbers and within four shots of the lead heading into round two. But there will be considerably less than that by the close of play on Friday with rough weather expected to hit the Southport links, producing some wild leaderboard fluctuations.

The weather forecast is for rain and drizzle throughout the day, with winds increasing from 25-30km an hour in the morning to nearly 40km an hour with 60km an hour gusts later in the day.