The move could worsen Ethiopia’s dispute with Egypt and Sudan over Grand Ethiopian Renaissance Dam, which Cairo says could threaten its main supply of water.

Ethiopia has banned all flights over an enormous dam it is constructing on the Blue Nile River for security reasons. the head of its civil aviation authority has said, as the country’s president said the project would start generating power in the coming 12 months.

Ethiopia, Sudan and Egypt have been locked in a bitter dispute over the filling and operation of the Grand Ethiopian Renaissance Dam (GERD), which remains unresolved although the reservoir behind the dam began filling in July.

“All flights have been banned to secure the dam,” the director-general of the Ethiopian Civil Aviation Authority, Wesenyeleh Hunegnaw, told the Reuters news agency by phone on Monday. He declined to give more details on the reasons behind the move, which could worsen the long-running dispute.

In a speech to Parliament later on Monday, Ethiopian President Sahle-Work Zewde said: “This year will be a year where the Grand Ethiopian Renaissance Dam will start generating power with the two turbines.”

She also said work was under way to enable a second filling of the giant hydropower dam within the next 12 months.

In July, Ethiopia said it had achieved its first year of filling the dam thanks to rainfall in the area.

Ethiopian Prime Minister Abiy Ahmed told the United Nations last month that the country has “no intention” of harming Sudan and Egypt with the dam, days after Egyptian President Abdel Fattah el-Sisi reiterated his concerns over the project.

Ethiopia, Egypt and Sudan failed to strike a deal on the operation of the dam before Addis Ababa began filling the reservoir behind it in July.

The dam is at the centre of Ethiopia’s bid to become Africa’s biggest power exporter.

The structure is about 15km (nine miles) from the Ethiopian border with Sudan on the Blue Nile – a tributary of the Nile River, which gives Egypt’s 100 million people about 90 percent of their fresh water.

The United States decided last month to cut $100m in aid to Ethiopia amid the dispute over the dam.

An unnamed US State Department official said at the time that the decision to pause some funding to Ethiopia was triggered by concerns over Ethiopia’s unilateral decision to start filling the dam before an agreement.