Andy Roddick continued his clashes with officialdom at the Australian Open Wednesday when he questioned an umpiring decision on match point in his victory over Brazil's Thomaz Bellucci.

The seventh seed had also collided with a line umpire in his first round match, which forced him to tumble to the ground. He admonished the line judge at the time.

Yesterday, Roddick held match point at 40-15 when a ball from Bellucci was adjudged to be in after review by the Hawkeye replay system. The big-serving American then produced what he thought was an ace to seal the victory, only for Bellucci to challenge the call.

Hawkeye determined the ball to be 'out', forcing Roddick to make a second serve.

However, Bellucci belted a forehand long in the subsequent rally to finally hand Roddick the 6-3, 6-4, 6-4 win.

Roddick then argued with chair umpire Fergus Murphy afterwards, with the American claiming he could have played the ball on his first match point. "I'm standing there with my racket back - don't you think I'm going to ... hit it?" Roddick shouted, adding a second profanity at the end. "It's not your job to predict if I'm going to hit it. It's your job to decide if I could hit it."

Then he reviewed the incident on video - and had a slight change of heart.

"There was just a disagreement about a rule I guess on a continuation of a call," he said. "To be fair, I didn't come in here (to the media conference) till I watched the video of it.

"I was more wrong than I thought I was out on court. That being said, it was very close. To take away a match point at that juncture in a match, it's a big call."

Roddick said after watching the video the decision was not as clear-cut as he thought it had been on court.

"I thought I was going to be 100 percent right. It's definitely closer than I felt it was while I was on court."

Roddick was more conciliatory on his Twitter page.

"Apologies for the language today folks hopefully most kids were asleep by the time I went off ...... my bad," he wrote, and also apologized for the handshake snub. "Did not realize that i didnt shake the umpires hand we were mid argument and i guess it didnt happen not a conscious decision."