Cairo will this week push Addis Ababa to agree to an outside mediator to help resolve a deepening dispute over a giant hydropower dam being built on Ethiopia’s Blue Nile, officials said on Sunday. Egypt fears the Grand Ethiopian Renaissance Dam will threaten scarce water supplies and power generation at its own dam in Aswan. It says it has exhausted efforts to reach an agreement on the conditions for operating the dam and filling the reservoir behind it, after years of talks with Ethiopia and Sudan. Ethiopia has denied that the talks are stalled, accusing Egypt of trying to sidestep the process. Egyptian President Abdel Fattah El Sisi is expected to raise the demand for a mediator when he meets Ethiopian Prime Minister Abiy Ahmed during a summit in Russia this week. “We’re hoping this meeting might produce an agreement on the participation of a fourth party,” an Egyptian Foreign Ministry official said. “We’re hopeful to reach a formula in the next few weeks.” Egyptian officials said they had suggested the World Bank as a fourth party mediator, but were open to a country with technical experience on water-sharing, such as the US. The EU was another option. Proposals by Egypt for a flexible filling of the reservoir and a guaranteed annual flow of 40 billion cubic metres were rejected by Ethiopia. The latest rounds of talks in Cairo and Khartoum over the past two months ended in acrimony. “The gap is getting wider,” the Egyptian official said. Egypt draws almost all of its fresh water from the Nile, and is faced with worsening scarcity for its population of nearly 100 million. It says it is trying to reduce the amount of water used in agriculture. Hydrologists consider a country to be facing water scarcity if supplies drop below 1,000 cubic metres a person each year. Egypt has about 570 cubic metres a person a year, which is expected to drop to 500 by 2025, without taking into account any reduction in supply caused by the dam, officials said. Ethiopia is expected to start filling the reservoir next year.