A leaked US embassy cable has revealed Egypt's fears about the possibility of its neighbour Sudan breaking into two.
In the cable, written last year, a foreign ministry official urged the US to help postpone a referendum on independence for Southern Sudan.
The official said the creation of "a non-viable state" could threaten Egypt's access to the River Nile.
Cairo's Almasry Alyoum newspaper published the cable, one of thousands being released by Wikileaks.
Southern Sudan is due to vote in a referendum on independence in January.
But in the cable - from the US embassy in Cairo - the official talks of implications should south Sudan secede and concern is expressed about the River Nile - a lifeline for Egypt.
Egypt has in the past threatened to go to war with any country tampering with the Nile.
The official said the creation of "a non-viable state" could threaten Egypt's access to the Nile at a time when several countries are negotiating how to share the river's water.
The official presses the US to help postpone the referendum by four to six years.
Egypt clearly fears a new nation, Southern Sudan, would be more likely to side with the upstream countries of the Nile basin like Kenya, Uganda and Ethiopia.
Vital resource
Those countries believe a colonial era treaty which guarantees that Egypt receives most of the Nile water is unfair.
Egypt and Sudan are refusing to sign up to a new agreement.
The fact that south Sudan is oil rich is seen as a major reason for tension ahead of the referendum on independence.
However, some argue that the vital water resource is likely to be a far greater bone of contention in the region long after the oil wells have dried up.
Wikileaks has so far released more than 600 of 251,000 classified US diplomatic and military cables.
