Fiery Australian Nick Kyrgios has been fined $7,500 for "spitting and audible obscenities" during his second-round win at the U.S. Open on Wednesday, tournament organizers told Reuters.

The fine was the largest handed out to a player at the tournament so far.

The Wimbledon finalist maintained a running dialogue with himself throughout his 7-6(3) 6-4 4-6 6-4 win over the Frenchman Benjamin Bonzi but boiled over when he was broken late in the fourth set.

He immediately spat in the direction of his players' box and swore at a man there he deemed as being insufficiently supportive.

"Go home if you're not going to (expletive) support me, bro," he shouted during the changeover.

"You are not a spectator."

Kyrgios also complained about the smell of cannabis during his night match at Louis Armstrong Stadium, saying he was concerned it could aggravate his asthma.

Fines for unsportsmanlike conduct are nothing new to the big-serving 27-year-old.

He was fined for spitting towards a fan after his first round win at this year's Wimbledon and again for swearing at an umpire during his heated fourth-round victory over Stefanos Tsitsipas.

Kyrgios is also being sued for defamation by a fan he accused of looking like she had "700 drinks" during his defeat in the final of the grass court major, where he also berated members of his players' box.