President George W. Bush on Thursday promised the US government would do everything possible to alleviate the chaos and suffering that has enveloped New Orleans and the Gulf coast in the wake of Hurricane Katrina, but acknowledged that federal and local authorities had not been prepared for the catastrophe.

As efforts continued to evacuate the flood-stricken city, which has been wracked by looting and other crime, Mr Bush said: “I don't think anybody anticipated the breach of the levees.”