'I want to help you': Umpire tells Kyrgios

Nick Kyrgios was told to try harder at the US Open on Thursday -- by a frustrated umpire who controversially climbed out of his chair to give the Australian a pep talk, telling him: "I want to help you".

Kyrgios was a set and 0-3 down to Frenchman Pierre-Hugues Herbert on Court 17 when umpire Mohamed Lahyani lost patience with the under-performing 30th seed.

"He was just concerned with the way I was playing," said Kyrgios after the match which he won 4-6, 7-6 (8/6), 6-3, 6-0, pocketing 19 of the last 25 games following Lahyani's intervention.

Lahyani had stunned the crowd when he stood over the seated Kyrgios, berating the 23-year-old in the second set.

"I want to help you," Lahyani could be heard saying to the player as questions on an official's impartiality began to be raised on social media.

"This isn't you. I know that. You are great for tennis."

At 2-5 down in the second set, Kyrgios even spent the changeover slumped in his chair with his arms behind his head, biting on a towel and fidgeting with his eyebrows as the second round clash appeared to be slipping away from him.

Richard Ings, a former umpires chief on the ATP, said Lahyani's move was unprecedented.

"I am racking my brain to think of a situation requiring a chair umpire to speak like that to one player," Ings tweeted.

"I umpired thousands of matches I was ATP head of officiating I can't think of one."

Croatia player Donna Vekic added: "Didn't know umpires were allowed to give pep talks."

Kyrgios has had a chequered history in the sport, picking up a series of fines and sanctions for his on-court behaviour.

At Wimbledon in 2015, he was accused of 'tanking' against Richard Gasquet.

At the 2016 Shanghai Masters, he was fined and banned for eight weeks for "lack of best efforts" against Mischa Zverev.

On his way to a 6-3, 6-1 loss in just 48 minutes in that games, he was heard to ask the umpire: "Can you call time so I can finish this match and go home?"

Kyrgios will next face either five-time champion and second seed Roger Federer or Benoit Paire of France for a last-16 spot.

"It'll be fun to play him and I will look forward to it," Kyrgios said of Federer. "If I play him, I will just go out there and try my arse off.