Sudan will only be willing to strike an interim deal with Ethiopia over its controversial Nile dam on conditions including an assurance of further talks, the water minister said on Monday.

Downstream Egypt and Sudan have been pushing upstream Ethiopia to ink a binding deal over the filling and operation of its massive dam on the Blue Nile that broke ground in 2011.

"Given the time constraints, Sudan will accept an interim agreement based on certain conditions which include signing on all the terms that have been already agreed,” Water Minister Yasser Abbas told reporters in Khartoum.

"There should also be guarantees that negotiations will continue ... and that those talks will be held within a defined timeframe.”

The minister said the three countries had already "reached consensus” over most technical matters but failed to reach a binding deal.

There had been "no development” in talks since African Union (AU) sponsored negotiations in Kinshasa in April.

Addis Ababa, which said it reached its first target of filling the dam last year, has announced it will proceed in July with or without a deal.

Egypt, which depends on the Nile for about 97 per cent of its irrigation and drinking water, sees the dam as an existential threat.

Sudan hopes the project will regulate annual flooding, but fears its own dams would be harmed without agreement on its operation.

Dozens of Sudanese protesters gathered outside the Italian embassy in Khartoum on Monday to protest the role of Italian contracting giant Salini Impregilo in the dam’s construction.

"We want to voice our rejection of the company’s role especially as there are not enough studies on the structure’s safety,” protester Walid Ali told AFP.

"If Ethiopia goes ahead with the second stage of filling, it will be catastrophic,” Ali said.

Last week, foreign and water ministers from Egypt and Sudan agreed at a meeting in Khartoum to "coordinate efforts... to push Ethiopia to seriously negotiate a deal”.

Last month, AU Chairman Felix Tshisekedi and the US envoy for the Horn of Africa, Jeffery Feltman, held talks with officials from Egypt and Sudan on the long-running dispute.

Sudan’s relations with Ethiopia have been also been hit by a dispute over the use of the Fashaga farmland near their common border.