Tennis bosses have vowed to fight a $US1.5 million ($A2.25 million) lawsuit being brought against them by Wimbledon champion Lleyton Hewitt.

Lawyers for Hewitt lodged papers in the South Australian Supreme Court on Wednesday suing the Association of Tennis Professionals (ATP), which runs the men's tour, for defamation following a dispute over the world number two's failure to do a television interview before a tournament in the United States last year.

Hewitt is claiming $US1 million ($A1.5 million) for lost international endorsements and sponsorship contracts, as well as $US500,000 ($A750,000) for his Australian losses.

The legal action comes just days before Hewitt begins the defence of his Wimbledon crown and stems from a long-running verbal battle sparked by the ATP's decision to fine Hewitt $US103,000 ($A150,000) for failing to do the interview.

Hewitt appealed and a three-member ATP appeals committee, chaired by a former US Federal appeals court judge upheld the ATP decision but reduced the fine to $US20,000 ($A30,000).

That failed to satisfy Hewitt, who said last month only a public apology from the ATP and an admission it had been wrong to fine him would prevent him from launching legal action.

ATP communication vice-president Matt Rapp said the lawsuit would be vigorously defended and accused Hewitt of needlessly prolonging the situation with the legal action.

"Although we have not been served with any papers, we understand from press reports that representatives of Lleyton Hewitt have formally filed legal action against ATP," Rapp said.

"The issue of proceedings reported today carries no substantive legal consequence, but is merely the next procedural step in accordance with Australian law.

"As stated previously, it would be unfortunate if this matter were pursued any further in the courts, needlessly prolonging a situation that should otherwise be concluded.

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