Nick Kyrgios says the ATP is "pretty corrupt" and added he is not worried about being suspended from the sport.
The world number 30 was fined $113,000 (£92,580) for his behaviour at the Cincinnati Masters, including swearing at umpire Fergus Murphy.
The ATP is yet to decide whether he has committed a "major offence" which could lead to a further fine or suspension.
"I was fined $113k for what?" the Australian said after beating Steve Johnson in the US Open first round.
"Why are we talking about something that happened three weeks ago, when I just chopped up someone first round of a US Open?