The South African firm will hold 51 percent stake while the Britain-based African Diamonds (AIM) will hold 49 percent in the new venture, a De Beers statement said.
"Upon completion of the first De Beers funded bankable feasibility study, De Beers interest will rise to 70 percent," it said, adding that the joint venture was subject to the approval of Botswana authorities.
African Diamonds said the "initial focus of the work will be on specific highest potential targets among the kimberlite pipes on the licences around Orapa," in northern Botswana.
"Work on the 1,000 square kilometre (400 square mile) licence north of the Orapa mine will commence in 2004 by airborne and ground geophysics and by the use of exploration techniques exclusive to De Beers," it said.
"A similar programme is planned for the Serowe licence currently held by African Diamonds, 120 kilometres (75 miles) southeast of Orapa."
Landlocked Botswana is the world's largest producer of gem-quality diamonds, which in 2002 accounted for 77 percent of its earnings and 45 percent of its gross domestic product. (AFP)