Egypt said it had protested to the UN Security Council against Addis Ababa’s plans to fill the reservoir of the controversial Grand Ethiopian Renaissance Dam (GERD) on the Nile river for a third year without agreement from downstream countries. Egypt "received a message from the Ethiopian side on July 26, stating that Ethiopia would continue filling the reservoir of the Renaissance Dam during the current flood season," a foreign ministry statement said Friday. In response, Egypt wrote to the Security Council "to register its objection and complete rejection of Ethiopias continuation of filling the Renaissance Dam unilaterally without a deal." The ministry stressed that Cairo maintains its "legitimate right... to take all necessary measures to ensure and protect its national security, including against any risks that Ethiopias unilateral measures may cause in the future." Addis Ababa deems GERD essential for the electrification and development of Africas second most populous country. But Cairo and Khartoum fear it could threaten their access to vital Nile waters and have demanded a written agreement between the three countries on the dams filling and operation. The new US envoy for the Horn of Africa, Mike Hammer, was in Ethiopia on Friday for talks that were expected to include the dispute over the dam. The envoy already held talks in Egypt on Monday. "We are actively engaged in supporting a diplomatic way forward under the African Unions auspices that arrives at an agreement that provides for the long-term needs of every citizen along the Nile," he said. During their recent meeting, US President Joe Biden reiterated to President Abdel Fattah Al-Sisi Washington’s support for Egypt’s water security and to forging a diplomatic resolution that would achieve the interests of all parties and contribute to a more peaceful and prosperous region, the US embassy said in a statement on Tuesday. The $4.2-billion dam is ultimately expected to produce more than 5,000 megawatts of electricity, more than doubling Ethiopias output. The first of 13 turbines began generating power in February. The process of filling the GERDs vast reservoir began in 2020, with Ethiopia announcing in July that year it had hit its target of 4.9 billion cubic meters. The reservoirs total capacity is 74 billion cubic meters, and the target for 2021 was to add 13.5 billion, a target Ethiopia said it had met.