'If the Iraqi military releases water into the Tigris River from upstream reservoirs, extensive flooding between Baghdad and Al-Kut could occur,' the department said in a statement. 'Thousands of Iraqis could be displaced, adding to congestion on roads and requiring extensive humanitarian support.'

The statement said that Iraq's strategy could include releasing a small amount of water from major dams and canals to interrupt manoeuvring units. Iraq also could cause catastrophic flooding of portions of the Tigris and Euphrates river valleys, either by releasing large amounts of water from dams or by destroying them, it added.

'The regime could incorporate the flooding into defensive preparations to slow the advance of coalition forces,' the department said. 'This tactic could force coalition units or displaced persons through flooded areas.'

The Al-Qadisiyah Dam and its Hadiyha Reservoir are the primary water sources for possible strategic flooding. There are five key reservoirs: Saddam, Dokan, Al Azim, Darbandikhan and the Diyala.