"I had a deal done for them and then, unfortunately, Ethiopia broke the deal, which they should not have done. That was a big mistake," Trump said.

"They will never see that money unless they adhere to that agreement," he said.

Egypt, Ethiopia and Sudan have been negotiating for nearly a decade to reach an agreement on outstanding issues related to the impact of the $4.6bn Grand Ethiopian Renaissance Dam (GERD) on their water security. 

Ethiopia says the project is indispensable for its electrification and development needs and has voiced hope of beginning operations in early 2021.

Egypt depends on the Nile for about 97 percent of its irrigation and drinking water and is concerned that the filling of the dam will exacerbate a water shortage crisis in the event of a prolonged drought. 

Sudan, Ethiopia's northern neighbour, has concerns regarding the potential impact of the construction of the dam on its own dams, and for the safety of its population and farmland from flooding that could result from faults in the construction or operation of the GERD. 

Sudan's Prime Minister Abdulla Hamdok, asked by Trump on speakerphone about the dam, voiced appreciation for US diplomacy and said his government wanted an "amicable solution soon" among the three countries.

The speed of the filling of the dam will potentially have an immediate effect on Egypt.