Serena Williams of the US argues with the chair umpire during her match against Samantha Stosur of Australia in the finals at the US Open tennis tournament in New York, Sept 11, 2011. [Photo/Agencies]

* Outburst came on last day of two-year probation

NEW YORK - Serena Williams escaped with a $2,000 fine on Monday when tennis officials ruled that her verbal abuse of an umpire during Sunday's US Open final was not a major offense.

The American was investigated by the Grand Slam Committee after she unleashed a torrent of abuse against Eva Asderaki, the Greek umpire who oversaw her shock loss to Australia's Sam Stosur.

Williams, who was on the last day of a two-year probation over an ugly incident at the 2009 US Open, could have faced a more severe penalty, including a hefty fine and a possible suspension, but officials took a lenient line.

US Tennis Association (USTA) tournament director Brian Earley fined Williams $2,000 and the Grand Slam Committee Director agreed that was a sufficient penalty.

"This fine is consistent with similar offenses at Grand Slam events," the USTA said in a statement. "After independently reviewing the incident which served as the basis for the code violation, and taking into account the level of fine imposed by the US Open referee, the Grand Slam Committee Director has determined that Ms. Williams' conduct, while verbally abusive, does not rise to the level of a major offense under the Grand Slam Code of Conduct."

Williams was investigated by officials after she was issued with a code violation for arguing with the umpire during her loss to Stosur.

Serena Williams of the US argues with the chair umpire during her match against Samantha Stosur of Australia in the finals at the US Open tennis tournament in New York, Sept 11, 2011. [Photo/Agencies]

The American lost her composure when she was docked a point for screaming "Come on!" just as Stosur was about to try and return a shot. She was then given a code violation after yelling at the umpire.

"If you ever see me walking down the hall, look the other way because you're out of control," Williams told the umpire. "You're out of control. You are unattractive inside.

"Code violation for this? I expressed myself, we're in America last time I checked. Don't look at me. Don't look my way."

Williams later said her comments were made in the heat of the moment and she had no reason to apologise but officials said they were taking a closer at the incident because Williams remained under probation for her foul-mouthed rant in 2009 during a semi-final loss to eventual champion Kim Clijsters.

She was fined $82,500 and warned that the fine would be doubled and she could be suspended from other grand slams if she committed another "major offense" in the next two years.