Novak Djokovic kept his cool in the New York heat to reach the semi-finals of the US Open and break yet another record.

The ice-cold Serbian is through to the last four of a grand slam for the 47th time, moving him one ahead of Roger Federer’s tally, after a 6-1 6-4 6-4 win over Taylor Fritz.

The roof was half-closed on Arthur Ashe to shield the players from the 90 degree temperatures amid energy-sapping humidity at Flushing Meadows.

American Fritz has been red hot all fortnight, not dropping a single set on his way to the last 16, but he was ruthlessly extinguished by the 23-time grand slam champion.

A demoralised Fritz has now lost all eight matches he has played against Djokovic.

The ninth seed hit more winners – 33 to Djokovic’s 25 – but he was simply ground down by the 36-year-old with a grand total of 51 unforced errors telling its own story.

He also forced 12 break points but converted only two of them, the second of which levelled the third set at 4-4 and prompted Djokovic to shoo some of his own supporters out of one of the executive suites.

But Djokovic immediately hit back, the three-time winner then saving another break point before completing the victory in two hours and 35 minutes to silence a partisan American crowd.

Djokovic said: “It’s expected that people are backing the home player, there’s nothing wrong with that. I like the atmosphere here, I’m fine with that and I thrive on that energy.

“I’ve been playing on this court for many years, played many epic matches, and I’m looking forward to another one in a few days.

“It’s a huge opportunity every time I step out on the court and at my age I don’t know how many more opportunities I’ll get.”

Djokovic later revealed he did not know the identity of the spectator he had gestured to leave the box, after admitting the man put him off by yelling during a point.

“Yeah. Yeah, he did. He was actually in the box where some of my friends were,” added Djokovic.

“I don’t know who the guy was, but yeah, I was pretty annoyed by him at that point. I was communicating with my friends to have a little chat with him.”

Djokovic will face big-serving American Ben Shelton for a spot in the final after the 20-year-old eclipsed compatriot Frances Tiafoe 6-2 3-6 7-6 (7) 6-2.

Speaking on-court after the match, Shelton said: “I felt like I left it all out here tonight. It was an emotional battle.”

The result makes Shelton the youngest American US Open semi-finalist in 30 years.