De Beers, the world's largest diamond miner, is shifting it aggregation and selling business to Gaborone, Botswana, from London.

"The agreement gives us direct access to market, which will be helpful for the successful development of the diamond industry in Botswana," said Ponatshego Kedikilwe, minister of minerals, energy and water resources.

The move of people and equipment to Gaborone from London before the end of 2013 under the 10-year agreement.

This means all the diamonds produced and sorted at its mines in SA, Namibia and Canada will be sent to Gaborone where they will be blended with those from Botswana, the world's single biggest source of rough diamonds ahead of sights, as sales are called, with about 70 carefully chosen clients from around the globe.

"De Beers has secured long-term and uninterrupted access to the largest supply of diamonds in the world," said De Beers chairman Nicky Oppenheimer.

The Botswana government has a 15% stake in De Beers and it is a 50% partner in Debswana. It has been pushing hard on beneficiation of diamonds, the key revenue generator for the landlocked nation.

De Beers produced 33 million carats last year and lowered its forecast for this year to 35 million carats from 38 million.