Sudan has condemned neighboring Ethiopia for launching power generation at a controversial dam on the Blue Nile without the agreement of downstream nations, saying the “unilateral move” violated international commitments.

The country “has emphasized its rejection of all unilateral measures with regard to filling and operation” of the Grand Ethiopian Renaissance Dam, the spokesman for its negotiating team, Omar Kamel, said in a statement late Monday. He said the Ethiopian move was a “fundamental breach” of its commitments under international law.

The other downstream nation, Egypt, which has been bitterly opposed to the dam project ever since construction started more than a decade ago, has also sharply criticised Ethiopia for starting up the turbines on Sunday. Multiple rounds of talks between the three governments since 2011 have failed to produce agreement on its operation.

The two downstream nations had also pushed for an agreement on the filling of the dam’s reservoir, but Ethiopia went ahead without one in 2020.

Addis Ababa regards the dam project which will be Africa’s largest when complete, as essential to the development of Africa’s second most populous country. Egypt, which depends on the Nile for about 97 percent of its irrigation and drinking water, sees the dam as an existential threat. 

Sudan hopes the project will regulate annual flooding, but fears its own dams will be harmed without agreement on its operation.