Best Buy Co., the largest U.S. electronics retailer, will open its first stores in Europe by paying $2.1 billion for a 50 percent stake in Europe's largest cell phone retailer, the companies announced Thursday.

The 50-50 venture will include Carphone Warehouse's 2,400 retail stores in nine European countries, the companies said in a statement. The assets will also include London-based Carphone Warehouse's share of an existing venture with Best Buy.

Current Carphone Warehouse shops will keep the Carphone Warehouse name. The new, larger stores that are opened in Europe will be branded Best Buy.

Carphone said on Thursday it would use the proceeds to help pay off some of its debt and make further investments in its telecoms network, broadband customer growth, infrastructure and other areas.

It is clear that we have a significant opportunity for incremental growth in our retail business which we can best realise with Best Buy on board, Charles Dunstone, Carphone's chief executive and largest shareholder said in a statement on Thursday.

Carphone Warehouse said it will continue as sole owner of its fixed line telecoms business in the United Kingdom, which includes TalkTalk, AOL Broadband and Opal; and its share of the Virgin Mobile France joint venture.

Best Buy will open stores under its brand name across Europe, beginning next year in the U.K.

Best Buy and Carphone Warehouse have a partnership to run Best Buy Mobile in the U.S. and Geek Squad, Best Buy's technical services unit, in Europe. Best Buy bought 3 percent of Carphone Warehouse last year.