Angola submitted a bid for a majority stake in diamond giant De Beers, a unit of Anglo American, according to a source familiar with the matter. The offer by state-owned diamond company Endiama sets up a potential standoff with Botswana, which also declared its intention to take full control. This marks a shift from Angola’s September stance of seeking only a minority stake. The bid challenges Botswana, which currently owns 15% of De Beers and considers it a strategic national asset. The potential sale comes amid a global slump in diamond prices.