CAIRO (AP) — Three key Nile basin countries on Sunday resumed online negotiations led by the African Union to resolve a years-long dispute over a giant hydroelectric dam that Ethiopia is building on the Blue Nile, Egyptian and Ethiopian officials said.


Years of talks between Egypt, Ethiopia and Sudan with a variety of mediators, including the Trump administration, have failed to produce a solution. The two downstream nations, Egypt and Sudan, have repeatedly insisted Ethiopia must not start filling the reservoir without reaching a deal first.


Egypt and Sudan suspended their talks with Ethiopia earlier this month, after Addis Ababa proposed linking a deal on the filling and operations of its Grand Ethiopian Renaissance Dam to a broader agreement about the Blue Nile's waters. That tributary begins in Ethiopia and is the source of as much as 85% of the Nile River.


The start of the online conferencing Sunday was announced in a tweet by Ahmed Hafez, a spokesman for Egypt’s Foreign Ministry, with attached photos of the Egyptian delegation taking part.


Ethiopia’s Water Minister Sileshi Bekele tweeted that the talks included the foreign and irrigation ministers of the three countries. Also taking part were AU Commission Chairman Moussa Faki Mahamat and South Africa’s Foreign Minister Naledi Pandor, whose country is the current chair of the regional block.


Neither Egypt nor Ethiopia announced a time frame for this round of talks.


The dispute over the dam reached a tipping point in July, when Ethiopia announced it had completed the first stage of the filling of the dam’s 74 billion-cubic-meter reservoir, sparking fear and confusion in Sudan and Egypt.


A colonial-era deal between Ethiopia and Britain, which at the time controlled Sudan and Egypt, effectively prevents upstream countries from taking any action — such as building dams and filling reservoirs — that would reduce the share of Nile water to downstream countries Egypt and Sudan.


To Ethiopia, the $4.6 billion dam offers a critical opportunity to pull millions of citizens out of poverty and become a major power exporter.


Egypt, which depends on the Nile River to supply its farmers and booming population of 100 million with fresh water, the dam poses an existential threat.


Sudan, geographically located between the two regional powerhouses, says the project could endanger its own dams — although it stands to benefit from it through having access to cheap electricity and reduced flooding.