Botswana, the world’s largest diamond producer, says it’s closely following BHP Billiton’s battle to buy Anglo American, which controls their diamond venture through De Beers.

President Mokgweetsi Masisi told CNBC Africa at the U.S.-Africa Business Summit in Dallas, Texas that while no-one had approached Botswana about the matter, the government would defend its interests in De Beers, in which it owns 15 percent. De Beers and the Botswana government jointly co-own Debswana Diamond, the largest diamond producer in the world by value.

“The value of De Beers is fundamentally created by Botswana. Without Botswana De Beers doesn’t exist,” he said in an interview with Fifi Peters.

Australian company BHP Billiton, the world’s largest miner, has offered about $39 billion for London-based Anglo American’s copper mines, minus its Botswana and South African assets in Debswana, Kumba Iron Ore and Anglo American Platinum. Anglo has rejected the overture arguing it undervalues its initiatives to unlock value for shareholders.

Analysts say BHP might be mulling a second bid and could face competition from commodities producer Glencore. South African Mines Minister Gwede Mantashe, who has met with Anglo executives, has said he is watching developments.

“Well, we remain laser focused on the developments because we clearly are an interested party,” he said. “I also want to state for the record that the value of De Beers is fundamentally created by Botswana. Because without Botswana, De Beers doesn’t exist.”

BHP has proposed that Anglo sell its shares in units Anglo Platinum and Kumba Iron Ore as an option to exit the South African assets it does not want included in the deal. It hasn’t pronounced on De Beers.