France, July 3 -- Ethiopia's Prime Minister Abiy Ahmed on Thursday said a multi-billion-dollar mega-dam on the Blue Nile that has long worried neighbouring countries is complete and will be officially inaugurated in September.

The Grand Ethiopian Renaissance Dam (GERD), launched in 2011 with a $4-billion budget, is considered Africa's largest hydroelectric project stretching 1.8 kilometres (wide and 145 metres.

Addis Ababa says it is vital for its electrification programme but it has been a source of tensions with downstream nations Egypt and Sudan who worry it will affect their water supply.

Speaking in parliament, Abiy said GERD "is now complete, and we are preparing for its official inauguration".

"To our neighbours downstream - Eg...