Addis Ababa has said it will fill the reservoir, a move that has been rejected by both Cairo and Khartoum.
Sudan has opposed an Ethiopian proposal to fill the Grand Ethiopian Renaissance Dam (GERD) on the Blue Nile for a second time, according to a senior official on Sunday.
Ethiopia hopes to facilitate the development and power generation on the GERD, leaving Sudan in a state of concern about the regulation of flow to its own dams, while Egypt fears an impact on its own water supply.
Addis Ababa said it plans to fill the reservoir behind the hydropower dam after seasonal rains start this summer.
However, this move has been opposed by Egypt and Sudan without a binding agreement on filling and operating the dam.
Sudan and Egypt sent letters asking the UN Security Council to take up the issue. Sudan has said that it is open to a partial interim agreement before the filling of the reservoir, with certain conditions.
The official also said that Ethiopia had placed “impossible conditions” related to the division of the share of the water, which Sudan considers outside the scope of negotiations.
Ethiopia shares the Blue Nile with Egypt and Sudan, and the Renaissance dam has long been the cause of a dispute between the three nations.
In recent weeks, disputes over the GERD have deepened.
Earlier this month, Ethiopia rejected a resolution by the Arab League which called for the intervention of the United Nations Security Council in the dispute, in a bid to mediate between Egypt, Sudan and Ethiopia.
Members of the Arab League held a special session on the long-disputed GERD in Qatar on June 15, where diplomats raised concerns over increasing tensions between Sudan, Egypt and Ethiopia.
In a joint statement, members stressed the importance of water security in Sudan and Egypt, saying it is an “integral part of Arab national security”.
Additionally, the statement called for reaching an “urgent, fair and balanced” consensus on the GERD that meets the interests of the three countries involved in the dispute.
“African mediation on the Renaissance Dam started about a year ago, but unfortunately it did not produce the desired results,” said Secretary-General of the Arab League Ahmed Aboul Gheit during a press conference.
“I sensed clear and strong Arab support for Egypt and Sudan, given that the security of the two countries is part of Arab national security,” he added.
The Arab League’s statement went on to express its concerns over Ethiopia’s intention to continue to fill the dam, describing it as a violation of international law as well as an agreement between the three countries signed in 2015.
“[The Arab League] demands Ethiopia to stop any unilateral decision that could harm the interests of Egypt and Sudan, including filling the dam without reaching an agreement,” added the statement.
Aboul Gheit also announced that the Arab League has assigned a committee at the United Nations to coordinate work with the international bodies on matters related to the dam.
The joint statement called on Tunisia, Arab member of the Security Council, and the committee in place—consisting of Jordan, Saudi Arabia, Morocco and Iraq—to intensify its efforts in the GERD file by continuing to coordinate with Sudan and Egypt.
Qatar has also assumed a mediating role in the GERD following requests from Khartoum and Cairo.