Andy Roddick has apologized for his use of profanity during an argument with the chair umpire that followed his 6-3, 6-4, 6-4 win over Thomaz Bellucci at the Australian Open.

"Apologies for the language today folks," wrote Roddick on his Twitter account. "Hopefully most kids were asleep by the time i went off ...... my bad.

"Also did not realize that i didnt shake the umpires hand[,] we were mid argument and i guess it didnt happen [--] not a conscious decision."

Roddick was disputing umpire Fergus Murphy's earlier decision not to replay a point overturned by a HawkEye challege. With Roddick holding match point at 5-4, Bellucci successfully challenged an out call that went against him. The umpire decided to award Bellucci the point, but Roddick said the point should be replayed because Bellucci's shot was not a clear winner.

"It's not your job to predict if I [w]ould have hit the ball or not, it's your job to say if I could have hit it," Roddick told Murphy after the match ended. That's bull*.

Walking back to his chair, Roddick added, "If I take my racquet back, don't you think I'm going to f*ing hit it?"

TV replays suggested Roddick may have had a play on the ball, but during his post-match press conference the American admitted, "To be fair, I didn't come in here till I watched the video of it. I was more wrong than I thought I was out on court."

Arguments with the chair are not infrequent for Roddick, who was involved in a similar situation with umpire Emmanuel Joseph during his third-round loss to Phillip Kohlschreiber in Melbourne in 2008. "I was one foot from the ball. I'm going to speak very slowly to you, so you can understand me," Roddick said, later adding, "Kids, stay in school or you'll end up being an umpire."

The same dispute also occured during a second-round match against Nicolas Mahut during Toronto in 2008, with Roddick afterwards saying he would have had to have "alligator arms not to get to that ball."

But Roddick was strongly criticized in local newspapers after Wednesday's match, with indications that Serena Williams' outburst at the U.S. Open has heightened sensitivity to players directing foul language at officials.

"[Roddick] used language of the colour and vulgarity spoken by Serena Williams in her US Open semi-final blow-up last year," said a column in The Australian. "Admittedly there was a small but significant difference between the incidents. Roddick did not threaten the umpire's life nor did he suggest he might stuff a series of tennis balls down his throat. Nonetheless, it was an unfortunate and unnecessary sign of cynical aggression from Roddick."

A column in the Melbourne Age said, "Angry Andy is not entitled to carry on, swear and attempt to claim victimhood... Tennis officiating is not a democratic process, or a negotiation, no matter what Roddick thinks. At 27, Rational Roddick needs to put his childish alter ego to bed."

Roddick will face some fine for use of profanity. At the U.S. Open, roger Federer was fined $1,500 for directing a swear word at the umpire, while Serena Williams was docked $10,000 for a profanity-laced tirade.