ADDIS ABABA (Reuters) -Ethiopia has completed filling the reservoir of its huge dam on the Blue Nile river for a second year, a minister said on Monday, a move that has already angered Egypt.

Addis Ababa says the Grand Ethiopian Renaissance Dam (GERD), a $4 billion hydropower project, is crucial to its economic development and to provide power.

But it has caused concern over water shortages and safety in Egypt and Sudan, which also depend on the Nile’s waters.

“The second filling of the Renaissance dam has been completed and the water is overflowing,” Seleshi Bekele, Ethiopia’s minister for water, irrigation and energy said on Monday.

“It means we have now the needed volume of the water to run the two turbines,” he said in a Tweet.

Earlier on Monday, state-run Ethiopian Broadcasting Corporation reported that the second round of filling the dam’s reservoir would be “completed in few minutes”.

Egypt said last month it had received official notice from Ethiopia that it had begun filling the reservoir for a second time and said it rejected the move.

Egypt views it as a grave threat to its Nile water supplies, on which it is almost entirely dependent. Sudan has also expressed concern about the dam’s safety and the impact on its own dams and water stations.

Long-running diplomatic efforts to resolve the dispute between the three countries have yielded little success.

The United States has also said Ethiopia’s filling of the dam had the potential to raise tensions and has urged all parties to refrain from any unilateral actions.

(Reporting by Dawit Endeshaw; Writing by Katharine Houreld and Elias Biryabarema; Editing by Andrew Heavens and Angus MacSwan)