With a major levee break finally plugged, engineers are struggling to pump out the flooded city as authorities braced for the horrors the receding water would reveal.
"It is going to be awful and it is going to wake the nation up again," the mayor said on Tuesday.
Mayor Ray Nagin said it would take three weeks to remove the water and another few weeks to clear the debris. It could also take up to eight weeks to get the electricity back on.
"I've gone from anger to despair to seeing us turn the corner," he said on NBC's Today. Still, he warned that what awaits authorities below the toxic muck would be gruesome. A day earlier, he said the death toll in New Orleans could reach 10,000.
The Army Corps of Engineers began pumping the water out after closing a major gap in a key levee that burst during Hurricane Katrina and swamped 80% of the bowl-shaped, below-sea-level city.
Efforts to evacuate holdouts were stepped up, with boat rescue crews and a caravan of law enforcement vehicles from around the country searching for people to rescue.
"In some cases, it is real easy. They are sitting on the porch with their bags packed," said Joe Youdell of the Kentucky Air National Guard. "But some do not want to leave and we can't force them."
Nagin warned: "We have to convince them to leave. It is not safe here. There is toxic waste in the water and dead bodies and mosquitoes and gas. ... Fires have been started and we don't have running water."
Evacuation efforts were stepped up
At the same time, the effort to get the evacuees back on their feet continued on several fronts.
Patrick Rhode, deputy director of the Federal Emergency Management Agency, said evacuees would receive debit cards so that they could begin buying necessary personal items.
He said the agency was going from shelter to shelter to make sure that vacuees received cards quickly and that the paperwork usually required would be reduced or eliminated.
In neighbouring St. Bernard Parish, officials expressed frustration that federal aid, slow to reach New Orleans, was even slower to get to outlying areas.
"This is Day Eight, guys. Everything was diverted first to New Orleans, we understand that. But do you realise we got 18 to 20 feet (5.5 to 6 metres) of water from the storm, and we've still got seven to eight feet (2 to 2.5 metres) of water?" said Ron Silva, a district fire chief.
"If you had dropped a bomb on this place, it couldn't be any worse than this."
"I have been all over the world. I have been in a lot of Third World countries where people were better off than the people here are right now."
Retired Air Force captain
In addition to help from other Louisiana and Alabama departments, a Canadian task force of firefighters and police arrived four days after the storm, St. Bernard Fire Chief Thomas Stone said.
"If you can get a Canadian team here in four days, US teams should be here faster than that," Stone said.
The frustrations also were being felt along the Mississippi coast, where people who have chosen to stay or are stuck in demolished neighbourhoods scavenge for necessities. Some say they will stay to rebuild their communities. Others say they would leave if they could get a ride or some gasoline.
But all agree that - with no water or power available, probably for months - they need more help from the government just to survive.
"I have been all over the world. I have been in a lot of Third World countries where people were better off than the people here are right now," retired Air Force Captain William Bissell said Monday.
"We have got 28 miles of coastline here that's absolutely destroyed, and the federal government, they're not here."
The scope of the misery inflicted by Katrina was evident on Monday as President George Bush visited Baton Rouge and Poplarville, Mississippi, his second inspection tour by ground.
"Mississippi is a part of the future of this country and part of that future is to help you get back up on your feet," Bush told 200 local officials.
US Health and Human Services Secretary Mike Leavitt declared a public health emergency for Texas, saying it would speed federal assistance to help almost 240,000 storm evacuees - the most of any state.
In New Orleans, Deputy Police Superintendent W.J. Riley estimated that fewer than 10,000 people were left in the city. Some simply did not want to leave their homes, while others were hanging back to loot or commit other crimes, authorities said.
Fewer than 10,000 are estimated
tobe left in New Orleans
Nagin said the city had the authority to force residents to evacuate but didn't say whether it was taking that step. He did, however, say that water will no longer be handed out to people who refuse to leave.
The leader of troops patrolling New Orleans declared the city largely free of the lawlessness that plagued it in the days following the hurricane. He lashed out at suggestions that search-and-rescue operations were being stymied by random gunfire and lawlessness.
"Go on the streets of New Orleans â€“ it is secure," Army Lieutenant General Russel Honore said to a reporter. "Have you been to New Orleans? Did anybody accost you?"
Britain is still trying to find 96 of its nationals in the United States, feared missing in the wake of Katrina, the Foreign Office said Tuesday.
A Foreign Office spokesman said that it was still trying to track down the whereabouts of 96 people after the 29 August disaster, but there had been no reported casualties so far.