ISTANBUL   Egypt on Tuesday said it has submitted a letter to the UN Security Council warning against Ethiopia’s unilateral operation of its new Nile dam, describing the move as a “breach” of international law. In the letter, Foreign Minister Badr Abdelatty said Addis Ababa’s inauguration of the Grand Ethiopian Renaissance Dam (GERD) was “an unlawful unilateral act” that cannot be legitimized. “Any misconceptions that Cairo would turn a blind eye to its existential interests in the Nile are