Egypt has rejected Ethiopia's statement justifying its absence from the talks over its giant Nile River dam project and its declining to sign a deal to settle the dispute.

Ethiopia's failure to attend the February 27-28 ministerial meeting with Egypt and Sudan in the US capital of Washington DC "deliberately" hindered the course of negotiations, the Egyptian ministries of foreign affairs and water resources said in a joint statement.

The statement cast doubt on Ethiopia's explanation that it needed more time to consider, "after more than five years of being fully engaged in intensified negotiations that tackled all dimensions and details of the issue".

Ethiopia, an upstream Nile Basin country, started building its Grand Ethiopian Renaissance Dam (GERD) in 2011 on the Blue Nile, raising concerns from downstream Egypt that the dam might affect its 55.5-billion-cubic-metre annual share of Nile water. 

While the Ethiopian team did not show up in Washington, Egypt on Saturday unilaterally signed a US-sponsored agreement that was supposed to be signed by itself, Ethiopia and Sudan.

The Ethiopian foreign ministry said in a statement on Saturday "the text reportedly initialled by the Arab Republic of Egypt in Washington DC is not the outcome of the negotiation or the technical and legal discussion of the three countries."  

It added that the guidelines and rules for filling and operating the GERD must be prepared by the three countries.