Wyndham Clark felt "everything was clicking" after storming into a strong lead in the first round of the US Open.

Clark, who won the tournament in 2023, finished six under par on Thursday with two holes remaining after play was suspended due to darkness.

The American currently holds a four-shot lead at the top of the leaderboard, thanks to back-to-back birdies at the third and fourth before an impressive eagle at the par-five fifth.

Clark could make history with his final two holes of the round; a birdie and par would see him equal the course record opening-round 63, while a birdie-birdie would see him level the lowest round in men's major history.

"Birdieing the first two was really nice," Clark said. "Then I had a little bit of a lull, but made some great par saves.

"It was great birdieing 18. Then a little mishap, missed a shorty on one and then a bogey on two, but then got into a nice rhythm. Everything was clicking."

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McIlroy featured earlier in the day, battling the tricky conditions to finish on one-under 69, leaving him tied-ninth.

The 2011 US Open winner was still pleased with his performance, believing it was about staying in contention more than anything.

"With the conditions today, anything under par or anything around even par is a good score," McIlroy said.

"It was a day to really keep yourself in the tournament and not shoot yourself out of it, which is exactly what I did eight years ago here [opening-round 80]."

Dustin Johnson and Gary Woodland are both tied-second on two-under with three holes remaining, with John Rahm also on the same score with five to go.

Matthew Fitzpatrick (two-under) has two holes remaining, while Max McGreevy, Ryder Cowan and Sam Stevens all shot two-under 68 to start the event.

World number one Scottie Scheffler, meanwhile, is struggled on Thursday with a two-over 72.