Harman, who is playing his first major since missing the cut in all four in 2015, fired six birdies and one bogey in a 67 to claim pole position in his bid to become the first left-handed winner of the US Open.

Fleetwood had been tied for the lead after birdies on the first, eighth, 12th, 14th and 15th, only to bogey the last after following up a poor pitch by putting his birdie attempt off the green.

"It was a good bogey though," joked Fleetwood, who regained his composure to hit a superb pitch from well below the putting surface. "That fifth shot on the 18th was the best shot all day.

"It was a really good round of golf and you don't realise until you start talking about it that I hardly missed a shot all day."

Asked about the prospects of emulating 2013 champion Justin Rose, the 26-year-old from Southport added: "It will change my life. I know that.

"I have pictured winning the US Open a lot of times before. Doing it all night is not going to help and not make any difference. It's just a question of concentrating on each day as it comes.

"Today I felt really good, played really well. If I wake up with the same feelings tomorrow I'm going to have a chance. Hopefully I do. I'll take it one step at a time.

"I don't think I could play any different or score any better than I have done. And you can't do anything about what anybody else is doing.

"If somebody shoots nine under tomorrow in the top few (as Thomas did on Saturday) then I'll have to shoot 10, I guess. But you can't do anything about that stuff. I've just got to keep going.

"This is my first time in contention in a major, so whatever happens I'll be doing my best and seeing how well I can finish. And that's all you can do. But it will be a pleasure to go out on a Sunday trying to win a major.

"It would be great to follow in Justin (Rose)'s footsteps. He's a good role model for English golf."