Ethiopia has said the US position on the controversial Nile River mega-dam project is "totally unacceptable".

The US is negotiating between Ethiopia and Egypt in the ongoing dispute over the Grand Ethiopian Renaissance Dam that some fear could lead to war.

Ethiopia accused the US of overstepping its role as a neutral observer after the US said the dam should not be completed without an agreement.

But its foreign minister said Ethiopia would continue to attend the talks.

Upon completion, the dam will be Africa's biggest hydroelectric power plant and provide Ethiopia and some neighbours with huge amounts of electricity and energy security.

The country wants to start filling the dam in June, but countries downstream are concerned about the impact on their water supply.

Egypt has viewed the project as an existential threat since construction began in 2011.

It relies on the Nile for 90% of its water, and a 1932 treaty gives Egypt and Sudan rights to almost all the Nile waters.