By Yolande Knell
BBC News, Cairo
Egypt believes it has a right to the lion's share of the water
"Egypt is the gift of the Nile," commented the Greek historian Herodotus back in the 5th Century BC.
The world's longest river, which runs through this desert country, produced its ancient civilisation and remains its main source of water.
But now Egypt is defending its historic rights to extract more from the Nile than any other country against calls for change to long-existing agreements.
"This is a national security issue," says Deputy Foreign Minister Mona Omar.
"The Nile is life for Egypt."
A 1929 agreement with Britain - representing its then East African colonies - gave Egypt the right to veto upstream projects that would affect its water share.
Egypt derives hydroelectric power from the great river
Another accord was signed by Egypt and Sudan in 1959.
It granted Egypt 55.5bn cubic metres of water every year - 87% of the Nile's flow.
Sudan was allocated 18.5bn cubic metres, the remaining 13%.
There have long been calls for change from other countries in the river basin: Burundi, Democratic Republic of Congo, Ethiopia, Eritrea, Kenya, Rwanda, Tanzania and Uganda.
Ethiopia, for example - the source of the Blue Nile - contributes an estimated 85% of the river waters but is able to make relatively little use of its natural resource.
After a recent meeting at Alexandria failed to resolve their differences, ministers from the nine main Nile states are allowing six months to agree a new legal framework for sharing water.
"We now have more time to negotiate the controversial issues between the countries: Egypt and Sudan on one side and the other seven countries on the other," says Ms Omar.
But she adds there is "no way" Egypt will allow a reduction of its water quota.
Ethiopia's Minister of Water Resources, Asfaw Dingamo, remains positive that the dispute can be overcome.
"Our negotiators and technical advisors will sit down and come up with a new arrangement," he says.
"In six months we can resolve all our differences."
The Nile Co-operative Framework Agreement would establish a permanent body to oversee river management.
It is seen as key to the future success of the Nile Basin Initiative (NBI) - an ambitious project to try to reduce regional tensions through joint economic development.
The World Bank supports the NBI, which was set up in 1997, and has already led to co-operative work on hydropower and irrigation schemes.
"The countries recognise that, without co-operation, if you add climate change and growing populations the future is a very unpredictable, risky one," says World Bank senior water adviser David Grey.
"With co-operation, the opportunities for joint development and management of the river system are very great and much more predictable for everybody."
Other experts argue large dams may exacerbate water-sharing problems along the Nile - and point out that many are being built independently of the NBI.
"All these competing projects combined with a dose of climate change could send the region's already over-tapped water resources to the brink of disaster," says Lori Pottinger from International Rivers Network (IRN).
"It's kind of like the Wild West in this watershed and I'm not at all sure that the NBI will be an effective sheriff."
IRN identifies the Nile Basin as a global hotspot for potential water conflict.
Several Nile countries are among the world's poorest nations and there is a history of fighting in and between them.
Water scarcity is already an issue but is becoming more pressing.
In Egypt a new official report predicts that if no action is taken the country's water needs will surpass its resources by 2017 because the population is still increasing fast.