Egypt, Sudan and Ethiopia's tripartite expert committee has delayed choosing a consulting firm to conduct an environmental impact study of Ethiopia's Grand Renaissance Dam, Egypt’s state news agency MENA reported on Monday.

Last year, the three countries agreed to choose a consulting firm to assess the environmental impacts of Ethiopia building the controversial dam on the Blue Nile, the Nile’s largest tributary.

The selection process has been ongoing for months.

Egypt has repeatedly voiced anxiety that the dam, to include a 74 billion cubic metre reservoir on the Blue Nile when finished, will adversely affect its water supply.

Addis Ababa has however claimed that the dam will not harm downstream countries Egypt and Sudan, and has continued construction.

Four consulting companies have been shortlisted and each country has examined their offers separately, Alaa Yassin, spokesperson for the Ethiopian dam issue at Egypt's irrigation ministry, told MENA.

In a third round of talks in Khartoum that ended on Sunday, the three countries concluded that several enquiries of the four companies should be answered before the final selection.

Sudan was assigned the task of following up with the companies, Yassin said.

It is not clear when a consulting firm will finally be selected, but the enquiries should be answered “within days”, he said.