Fresh off a drama-laden straight-sets victory over American Steve Johnson to reach the second round at Flushing Meadows, Kyrgios spoke for the first time about the hefty fine he copped for a spectacular meltdown at the Cincinnati Masters.

"The ATP is pretty corrupt anyway. I'm not fussed about it at all," Kyrgios told reporters after his late-finishing match on Louis Armstrong Stadium.

"I was fined 113,000 K for what? Why are we talking about something that happened three weeks ago when I just chopped up someone first round of a US Open?"

The following morning, however, Kyrgios moved to clarify his comments - accusing the ATP of "double standards" rather than "corruption" - as they confirmed Kyrgios' claim would be investigated under the Player Major Offence provision of their rules.

The volatile Australian was asked what he thought about being fined a record $US113,000 ($167,000) for his antics in Cincinnati, in which he called Irish umpire Fergus Murphy a "potato" and "f***ing tool", spat in the umpire's direction and broke two racquets.

On Wednesday morning, Kyrgios took to Twitter "to clarify my comment around the ATP being corrupt" and admitted that his behaviour "at times ... has landed me in trouble".

"I would like to go on record to clarify my comment around the ATP being corrupt, it was not the correct choice of words and my point and intention was to address what I see as double standards rather than corruption," Kyrgios said.

"I know my behaviour at times has been controversial and that has landed me in trouble, which at times is granted and valid but my issue is around others whether gaining the same, less or more media attention doing the same or similar behaviour and not being sanctioned.

"That's my issue and it continues to be. To be clear I know I'm not perfect and do not pretend to be and I acknowledge I've deserved fines and sanctioning at times but I expect consistency and fairness.

In addition to the fine Kyrgios copped in Cincinnati, the ATP was already considering banning the two-time major quarter-finalist for a second time in his career.

His latest allegations appeared almost certain to force his employers' hand and earn him an enforced break from the game.

What happens now after the 24-year-old softened his accusations against the ATP remains to be seen.

"The comments made by Nick Kyrgios after his first round match in New York will be assessed under the Player Major Offense provision under ATP Rules," said the men's governing body.

"A determination will be made by Gayle David Bradshaw, Executive Vice President, Rules & Competition, following an investigation as required by ATP rules."

The 2019 ATP Rule Book says a "major offence" may be punished by a fine of up to the amount of prize money won at a tournament and a suspension of up to a year.

Kyrgios has a lengthy rap sheet stretching back four years.

But US Open officials had given him the green light to play the final grand slam of the year despite tennis chiefs continuing to weigh up whether or not the temperamental talent should be rubbed out for his most recent outburst.

Kyrgios was slapped with separate penalties for an audible obscenity, ball abuse, verbal abuse towards the umpire, leaving the court and four counts of unsportsmanlike conduct during his explosive second-round loss to Russian Karen Khachanov in Cincinnati two weeks ago.

Despite being under scrutiny at Flushing Meadows, Kyrgios was unrepentant after progressing to the second round in straight sets.

When he was asked if he should have been defaulted in Cincinnati and, therefore, avoid being fined, the Australian engaged in an exchange with a journalist as his agent John Morris and an ATP press official tried to cut short the post-match media conference.

"Have you ever sworn at someone before?" he countered at a journalist.

"You're not an elite athlete."

Asked if he was saying it was acceptable for elite athletes to swear, Kyrgios said: "No, I'm just saying people get frustrated. It happens."

Kyrgios has already been banned once, in late 2016 after tanking in Shanghai, and ordered to undergo counselling.

In a year of ups and downs - Kyrgios has won two hardcourt titles in 2019 - the Australian was also defaulted from a match at the Italian Open in May after throwing a chair across the court.

Adding to Kyrgios's troubles on Tuesday night, a fan tweeted vulgar video footage of him courtside after his win.

"Always classy Nick Kyrgios. Wipes his sweat, crotch, armpits, then spits in a towel, right before throwing it to some fans. Real cool @NickKyrgios ?? the fan posted.

The US Open is run independently but a USTA official said pre-tournament that organisers of the season's final grand slam would follow the ATP's lead when asked if Kyrgios could be banned.

Kyrgios will play Frenchman Antoine Hoang on Thursday for a place in the last 32, a stage of the tournament he has reached three times - in 2014, 2016 and 2018.