Briton's Kyle Edmund took a set off top seed Novak Djokovic but ultimately struggled to keep up with the world number one's intensity, losing in the US Open second round.

But the 33-year-old maintained the level that has helped him stay unbeaten in 2020 and won 6-7 (5-7) 6-3 6-4 6-2.

Djokovic is seeking his 18th Grand Slam title and fourth US Open win.

He will face German 28th seed Jan-Lennard Struff in the third round.

"Overall it was a very good test and I'm happy to get through," Djokovic said. "Kyle played a fantastic first set. He didn't do much wrong. It was anybody's game really."

Edmund unfazed in first set

Djokovic has looked imperious all year, winning January's Australian Open and, more recently, the Western and Southern Open on Saturday.

But British number two Edmund looked unfazed and used his characteristically powerful forehand on Arthur Ashe.

Djokovic repeatedly turned to drop-shots, but the tactic was fruitless as the Briton saw them coming every time in a high-quality first set.

Things looked risky for Edmund as a sudden burst of intensity took the Serb to 30-0 up at 5-5 but the world number 44 composed himself to hold.

Djokovic held to love to take it to a tie-break, where a 100mph forehand winner and an ace down the middle were two highlights for Edmund en route to winning the set with compatriots Andy Murray and Dan Evans watching from the stands.

Djokovic handles the heat to turn the tide

The world number one did not look as commanding as usual, perhaps due to fatigue from just one day of rest after the previous tournament or distraction from plans to front a new association aiming to increase the power of the players.

But Edmund looked increasingly uncomfortable in the heat, changing between games as his kit had become soaked because of the humidity in New York.

"You could see how much both of us were sweating.," Djokovic said after the match. "That's Grand Slam, best-of-five matches."

The top seed kept his cool nevertheless. A double fault put him a break up and he went on to serve for the set, sealing it with an ace out wide.

Both players' levels dropped in an error-strewn third set. Edmund fought to save one break point early on, but his backhand sailed long to give Djokovic a 2-1 lead.

Djokovic won 11 points in a row to break a second time, though Edmund took advantage of a short second serve to claw a game back.

The top seed ran forward to pick up a drop-shot and tapped it past Edmund to go 5-2 up and eventually held to love to win a second set.

World number one 'brings the energy' to seal victory

Looking increasingly like the player that has won 24 games in a row this year, Djokovic roared as Edmund sent the ball into the net to lose his first service game in the fourth set.

The eight-time Australian Open winner's volume continued to increase as he shouted "there's so much energy in here" to an empty stadium after holding serve to take a 3-1 lead.

"We miss the fans. We miss the noise and the energy," Djokovic explained afterwards. "I like to bring the energy on court."

A backhand wide gave Djokovic another break and he served two aces and landed an easy smash for yet another hold to love and victory.

Edmund's exit leaves three British men in the draw, with Cameron Norrie also playing on Wednesday and Murray and Evans in action on Thursday.