NEW YORK (AP) _ The Warnaco Group Inc. offered to buy Authentic Fitness Corp. for $20.50 a share cash, or about $412 million.

The offer, announced Sunday, represents a 16.7 percent premium over Athletic Fitness's closing price Friday of $17.56 1/4, down 12 1/2 cents, on the New York Stock Exchange. Warnaco also would assume $113 million in debt.

Shares of New York-based Warnaco closed Friday at $17.43 3/4, down 12 1/2 cents, also on the NYSE.

Warnaco said Sunday the deal would immediately increase its earnings per share.

Warnaco is a marketer of underwear to U.S. department stores. It's brands include Calvin Klein, Olga and Warner's. The company had 1998 sales of $1.95 billion.

Authentic Fitness makes swimwear, accessories and other fitness apparel under the Speedo, Anne Cole and Catalina brands. The Commerce, Calif.-based company had sales of $410.8 million for the year ended July 3.