Sudan and Egypt agreed on Wednesday to coordinate efforts to push Ethiopia to negotiate "seriously" on an agreement on filling and operating a giant dam it is building on the Blue Nile, a joint statement said.
The two countries, which are downstream from the dam, issued the statement after African Union-sponsored talks remained deadlocked.
Ethiopia is pinning its hopes of economic development and power generation on the Grand Ethiopian Renaissance Dam (GERD). Egypt fears the dam will imperil its water supply and Sudan is concerned about the impact on its own water flows.
Talks overseen by the AU, aimed at reaching a binding agreement, have repeatedly stalled.
At talks in Khartoum, the Sudanese and Egyptian foreign and irrigation ministers agreed on "coordinating the efforts of the two countries at the regional, continental and international levels to push Ethiopia to negotiate seriously", the joint statement said.
Both countries blamed the failure of AU-sponsored talks on what they described as Ethiopia's intransigence.
Ethiopia has said it plans to complete the second phase of filling the dam in the coming rainy season, a move Sudan and Egypt rejected before a binding legal agreement was reached.
Egypt and Sudan called on the international community to intervene "to ward off risks related to Ethiopia’s continued pursuit of its policy of seeking to impose a fait accompli on the downstream countries".
There was no immediate response from Ethiopia, which has rejected calls from Egypt and Sudan to involve mediators outside the African Union.
Sudan said Ethiopia began the second phase of filling the reservoir behind GERD in early May.