Serena Williams has issued a public apology for the angry outburst at a lineswoman during her US Open semi-final defeat to Kim Clijsters.

Williams – who has been hit with a $10,000 fine, the maximum possible for an on-court code violation – admitted she "handled [herself] inappropriately" after she was called for a foot fault on a second serve that led to a match point against her.

The American shouted at the lineswoman for making the call, which was reported to the umpire who awarded a point to Clijsters that consequently ended the match.

"I want to sincerely apologise first to the lines woman, Kim Clijsters, the USTA, and tennis fans everywhere for my inappropriate outburst," Serena stated.

"I’m a woman of great pride, faith and integrity, and I admit when I’m wrong.

"I need to make it clear to all young people that I handled myself inappropriately and it’s not the way to act – win or lose, good call or bad call in any sport, in any manner."

Williams said she "likes to lead by example" and said she would "learn and grow from this, and be a better person as a result".

Clijsters went on to beat Denmark’s Caroline Wosniacki in the final to become the first mother to win a grand slam title since 1980.

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