Sudan and Egypt have grown increasingly concerned by Ethiopia's stance during negotiations over the Grand Ethiopian Renaissance Dam. The gravity dam on the Nile has been under construction since 2011.
The latest round of talks between Egypt, Ethiopia and Sudan over the Grand Ethiopian Renaissance Dam (GERD) appeared to have broken down on Tuesday.
The three sides are all seeking to find some common ground but Egypt's Foreign Ministry said in a statement that Ethiopia had a "lack of political will to negotiate in good faith."
Hosted by the Democratic Republic of Congo (DRC) in Kinshasa, the meeting between the three countries' foreign ministries began on Sunday and were extended into a third day on Tuesday.
To further complicate proceedings, a Congolese mediator said Sudan had objected to the terms of a draft communique, news agency AFP reported.
"Ethiopia and Egypt accepted the terms contained in the draft final communique. But Sudan felt that its interests in the River Nile were at threat," the DRC source, who spoke on condition of anonymity, told AFP.
Delegations from the three countries were hoping to find a breakthrough in negotiations over a project Ethiopia says is key to its economic development.
Grave concerns downstream
However, the other parties remain uncertain over the GERD. Egypt fears the dam will endanger its supplies of Nile water, while Sudan is concerned about the dam's safety and water flows through its own dams and water stations.
Egypt had said this latest meeting represented the last chance to re-start negotiations before Ethiopia begins to fill the dam for the second year in a row, after seasonal rains begin this summer.
Ahead of the latest round of talks, Egypt's President Abdel Fattah el-Sissi said there would be "inconceivable instability in the region" if his country's water supply were affected by the dam.
The Nile, the world's longest river by some people's calculations and one of the two longest by anybody's, remains crucial to keeping Africa fed and watered. Roughly 19 in 20 Egyptians live within a few kilometers of the river's banks and rely on its water.
Sudan and Ethiopia at loggerheads
Meanwhile, Sudan's foreign minister Mariam al-Sadig al-Mahdi said on Tuesday that Ethiopia's insistence on such unilateral moves represented a violation of international law.
"Without a new approach to negotiations, there becomes space for Ethiopia to impose a fait accompli and put all the peoples of the region in grave danger," said al-Mahdi.
Sudan and Egypt agreed on a proposal to include the European Union, the United States and the United Nations in the talks, as well as African Union mediators.
But Egypt said Ethiopia rejected the proposal during the meeting, as well as other suggestions to re-start negotiations.
Sudan is also in the midst of a border dispute with Ethiopia.