Ethiopia has refused to halt work on a controversial giant dam across the river Nile that Egypt fears will severely curb its water supply.
The refusal came after the Egyptian president, Mohamed Morsi, promised to "defend each drop of Nile water with our blood" and other senior Egyptian politicians called for the dam's destruction.
A spokesman for the Ethiopian prime minister said on Tuesday that Morsi's speech was irresponsible and that the project would proceed as planned.
"Nothing is going to stop the Renaissance Dam. Not a threat will stop it," Getachew Reda said via telephone. "None of the concerns the Egyptian politicians are making are supported by science. Some of them border on what I would characterise as fortune-telling."
Ethiopia hopes its Grand Renaissance dam – which will cost more than $4.3bn (£2.8bn) – will form Africa's largest hydropower plant. But Egyptian authorities have contested its construction after water experts claimed it would drastically lower the level of the Nile, which supplies almost all of Egypt's water, and could reduce cultivated farmland by up to 25%.
In a speech to Islamist supporters on Monday night, Morsi called the Nile "God's gift to Egypt", and ambiguously veered between calls for peaceful dialogue, and veiled military threats. He said that while Egypt did "not want war … we do not accept threats to our security", and claimed that all possible responses to the dam remained open to Egypt – a line that has been interpreted as a threat of force.
Last week, other senior Egyptian politicians were filmed discussing aggressive measures against their upstream neighbours – apparently unaware that their discussion was being broadcast live. Younis Makhyoun, the leader of Egypt's second largest political grouping, the ultraconservative Nour party, suggested to Morsi in a televised meeting that as a last resort Egyptian intelligence forces could destroy the dam. In response to the embarrassing gaffe, Ethiopia summoned the Egyptian ambassador in Addis Ababa to explain Egypt's stance.
Morsi's own aggressive speech is aimed at a domestic audience as much as a foreign one, as he seeks to regain support ahead of anticipated large protests against his presidency on 30 June. However insincere his military threats may be, they are nevertheless rooted in very real and widely held Egyptian fears about the dam's effect.
Dr Bahaa Alkoussey, the former chairman of Egypt's National Water Research Centre, and a one-time senior official in the ministry of water resources and irrigation, claimed the Ethiopian plans copuld reduce waterflow to Egypt by more than 10bn kilolitres.
"Then you might cross the Nile on the back of a camel," he said. "It's not a joke. This is a serious matter. The Egyptians already have a deficit in their water supply of about 10bn kilolitres. If you add just 1 kilolitre to that, it will be a disaster. Now it's already a problem. If you add more reductions, then you'll have a catastrophe."
Alkoussey claimed the dam would make it harder for ferries to travel up the Nile, and would cause more pollution, harming fish farms.
Most seriously, Alkoussey claimed the dam would devastate the farming community. "Every 1bn kilolitre reduction in natural flow to Egypt will cause 200,000 feddans [207,600 acres] of land to go out of production, and 500,000 farmers to be out of work – which will affect 2.5 million families," he said.
Supporters of the dam have argued that Egypt could solve the crisis by using its water more efficiently. But Hani Raslan, an expert on water politics at Cairo's government-affiliated Al-Ahram Centre for Political and Strategic Studies, argued Egypt recycled much of its water. "Egypt is one of the most efficient countries with water consumption," he said. "Our supplies are 55bn cubic meters but we consume 70bn, which means we're recycling 15bn cubic meters."
Ethiopia disputes the Egyptian experts' conclusions, claiming the dam has been largely exonerated by a recently completed, but as yet unreleased report written jointly by scientists from Egypt, Ethiopia and Sudan.
"Of course we are going to go ahead with the project, because we believe we are justified," Reda said. "Why would a self-respecting government spend $4.5bn simply to spite Egypt? It's beyond reason and it's beyond science. None of the concerns of the Egyptians [are] really something you can remotely associate yourself with."