World no 1 Lleyton Hewitt has threatened to sue the Association of Tennis Professionals for A$2.5 million [US$1.5 million].

Hewitt, 22, was fined US$106,000 for failing to attend a television interview shortly before he was due to play a match in Cincinnati last year. The fined was reduced to US$20,000 on appeal in January.

According to a report in the Daily Telegraph newspaper on Tuesday, Hewitt's lawyers have threatened to sue if the ATP does not drop the fine. 

Hewitt alleges that the ATP breached its contract with him and defamed him.

He also feels that the ATP 'intentionally and without justification' interfered in his business affairs by withholding part of his prize money. 

Hewitt's lawyers said they would begin proceedings in the South Australian Supreme Court in June unless the matter is resolved privately. 

Hewitt's father Glynn told the newspaper that the legal action is not about money, but protecting his son's reputation.

"The ATP does not seem to recognise this... It should be understood that the issue is, and always has been, about clearing Lleyton's name."