NEW YORK (AP) -- Martina Hingis, the world's top-ranked female tennis player, has filed a $40 million lawsuit charging that an Italian sportswear maker whose products she endorsed gave her shoes that injured her feet.

Hingis, 20, of Switzerland, says in court papers that in tournaments from 1996 into 1999, she wore clothing and shoes made by Sergio Tacchini as part of a five-year endorsement deal that was to pay her $5.6 million.

But because Tacchini had outfitted her with ``defective'' shoes ``unsuitable for competition,'' she was forced to withdraw from several tournaments, court papers say.

While competing in the U.S. Open in New York City in September 1998, Hingis sustained a debilitating foot injury, say papers filed in Manhattan's state Supreme Court.

Hingis had her feet examined by a Manhattan doctor, ``who confirmed that the injury was a chronic one and was being caused by the tennis shoes manufactured by the defendant Sergio Tacchini,'' court papers say.

``The shoes were defectively designed and manufactured and therefore were not providing Hingis with the support necessary to play competitive tennis,'' according to Hingis' court papers, filed Friday.

In October 1998, Hingis withdrew from tennis tournaments in Filderstadt, Germany, and Zurich, Switzerland. That same month, she had her feet examined by an orthopedic specialist -- recommended by Tacchini -- in Milan, Italy.

The doctor recommended that Tacchini modify Hingis' shoes, but the company, headquartered in Novara, Italy, failed to do so, court papers say.

Meanwhile, from October 1998 to June 1999, court papers say, Hingis' feet kept hurting.

``She was forced to receive treatments for her foot injuries at nine separate tournaments in Manhattan, Philadelphia, California and South Carolina,'' according to Hingis' lawsuit. ``Hingis also withdrew from the Wimbledon doubles tournament in June 1999 because of her injured feet.''

Then, in a letter dated April 23, 1999, Tacchini fired Hingis as a spokeswoman. Court papers said the company ``erroneously'' claimed she had breached their contract by failing to wear a Tacchini hat at a tournament and other Tacchini tennis clothing at a charity event.

In a press release that Hingis' court papers called ``false and defamatory,'' company chairman Sergio Tacchini explained why she was dropped.

``She damaged our image and our products because of her behavior and extremely discrediting statements concerning her main sponsor,'' court papers quote Tacchini as saying. ``We could not tolerate this attitude any longer.''

There was no listed representative for Tacchini in North America.