Egyptian President Mohammed Morsi has said “all options are open” to deal with any threat to his country’s water supply posed by an Ethiopian dam.

Mr Morsi said he was not “calling for war”, but that he would not allow Egypt’s water supply to be endangered.

Egypt was apparently caught by surprise when Ethiopia started diverting the Blue Nile last month, amid works to construct a hydroelectric dam.

The river is a tributary of the Nile, on which Egypt is heavily dependent.

The Great Ethiopian Renaissance Dam is a $4.7bn (£3.1bn) project that Ethiopia says will eventually provide 6,000 megawatts of power.

It says the Blue Nile will be slightly diverted but will then be able to follow its natural course.

“Egypt’s water security cannot be violated at all,” Mr Morsi said on Monday. “As president of the state, I confirm to you that all options are open.”