President Bush is to ask Congress for more than $50bn (£27bn) in extra emergency funding to deal with the aftermath of Hurricane Katrina.
The money - on top of $10bn that has already been granted - is slated for rescue efforts, clean drinking water, and public health needs.
New Orleans' mayor has ordered the forced evacuation of citizens refusing to leave, as health fears grow.
The authorities say five people have died from contaminated floodwater.
They apparently contracted infections after coming into contact with cholera-related bacteria in the water.
The US Environmental Protection Agency says the floodwaters contain unsafe levels of E.coli and other bacteria as well as high levels of lead.
As water is pumped out of New Orleans, the diminishing flood reveals dead bodies, raw sewage, fuel and rusting vehicles - nine days after Hurricane Katrina hit.
Up to 10,000 residents may still be in the city, but Mayor Ray Nagin says all but those involved in the rescue effort should leave.
Thousands of people are estimated to have been killed by Hurricane Katrina in New Orleans and the Gulf Coast, and hundreds of thousands are living in temporary shelters in Texas and other states.
Spokesman Scott McClellan said the White House was "sparing no effort" to help the victims of the hurricane, and that the new $51.8bn aid package would not be the last.
Mr Bush had hinted there would be a substantial aid package when he described the $10.5bn in congressional aid he signed off last week as a "downpayment".
Most of the new aid package will go to the Federal Emergency Management Agency (Fema), with $1.4bn for the military and $400m for army engineers repairing floodwalls in New Orleans.
Meanwhile, it has emerged that some 400,000 jobs could be lost this year because of the hurricane.
The Congressional Budget Office estimate comes as the economic impact of Katrina is put at more than $100bn (£55bn).
US Treasury Secretary John Snow has said the effect on the wider economy could be to stifle US growth by half a percentage point - although rebuilding work might actually boost the economy in 2006.
Mayor Nagin issued his emergency evacuation declaration late on Tuesday, authorising police and military to remove anyone who refused to leave their homes.
Soldiers and police fill the city, moving about in long convoys of military lorries, Humvee jeeps and commandeered buses along streets which are unlit at night because there is no electricity. Police cars cruise by, their lights flashing silently.
Looting has been widely reported in New Orleans and many householders are fearful of losing their possessions if they leave.
Presidential and Congressional plans for inquiries into how the disaster was handled have been questioned by the opposition Democrats, who have raised the idea of an independent commission.
President Bush said on Tuesday he would lead an investigation himself as two Senate committees began separate inquiries.