UN chief António Guterres is encouraging Egypt, Ethiopia and Sudan to persevere with efforts to overcome their differences and reach agreement on the Grand Ethiopian Renaissance Dam.

Negotiations centre on the pace at which Ethiopia fills the 74 billion cubic metre reservoir behind the dam and the impact that could have on water supplies downstream in Sudan and Egypt.

UN experts say that Egypt wants to put international pressure on Ethiopia to agree to a proposal - put forward by the United States and World Bank - on the dam's first filling and annual operation.

Egypt also insists that Ethiopia must not start filling the reservoir until an agreement is reached, in line with its interpretation of the Declaration that Ethiopia is contesting.

According to news reports, Egypt also dismissed the Ethiopian proposal on the initial filling, writing a letter to the Security Council on 1 May calling on Ethiopia to respect its obligations and resume talks.