A new dam on the Nile could trigger a war over water unless Ethiopia can agree a deal with Egypt and Sudan, writes the BBC's Africa Correspondent Alastair Leithead.

It is often said the world's next world war will be fought over water and there are few places as tense as the River Nile.

Egypt and Ethiopia have a big disagreement, Sudan is in the middle, and a big geopolitical shift is being played out along the world's longest river.

There's been talk about a dam on the Blue Nile for many years, but when Ethiopia started to build, the Arab Spring was underway and Egypt was distracted.

"Egypt was the gift of the Nile" the pharaohs said, and they worshiped the river as a god.

Read more on bbc.com.