FRANKFURT, Germany — Adidas-Salomon AG said today that it will buy shoemaker Reebok International Ltd. in a $3.8 billion deal, giving the company about 20 percent of the U.S. market and putting it in a position to better challenge leader Nike Inc.

Under the terms of the all-stock deal, Adidas will pay $59 a share for all of Reebok's outstanding shares, a premium of 34.2 percent.

The deal is subject to regulatory approval in the United States and Europe, along with that of shareholders. Both companies said the transaction could close during the first half of 2006.

The deal will bring together two impressive stables of athletes and entertainment endorsers. English soccer star David Beckham and rap artist Missy Elliott are under contract to Adidas.

In February, Canton, Mass.-based Reebok launched the "I am what I am" marketing campaign, which features pitches from celebrity entertainers and athletes in an effort to draw younger buyers who regard sneakers as high fashion. One of the ads featuring the rapper 50 Cent was pulled in March amid complaints that it glorified gun violence.

The announcement came as the Herzogenaurach-based company posted a 30-percent gain in second-quarter net profit and improved sales.