The relief operation on the southern coast of the United States is now in full swing, with troops bringing food and water to some of the thousands of stranded people in New Orleans.
President Bush has cleared his diary for the coming week to oversee relief operations, amid mounting criticism of the aid effort.
BBC correspondents report on the latest developments from the worst-hit areas of Louisiana and Mississippi.
Saturday Sept 2
David Willis, Gulfport, Mississippi, 2255GMT
A week after Katrina struck and she is still claiming victims. It is hot here and bothered by a shortage of food and water. People look bewildered. At the local funeral home they are struggling to cope. Mobile mortuaries have been brought in to deal with the dead.
Many elderly people are struggling without their medicines, lost amongst the rubble and unable to get replacements, they continue to struggle with the heat and the stress.
Adam Brookes, New Orleans, Louisiana, 2210GMT
In the dying city of New Orleans the military appears finally to be taking charge of these squalid streets. Convoys nose their ways into the city. Where I was the distribution was calm and orderly.
This aid started pouring into the centre of the city on Friday afternoon and it is starting to make a little difference to these poor desperate people still stranded here, six days after the hurricane. At least now they will not die of dehydration in this blinding heat.
But nothing will assuage the anger. Most of the streets are still under water and we know next to nothing about what has happened in the flooded areas.
They are still evacuating hospitals which are just half a mile from dry land. Patients who survived the storm and six days without power or water, and with dwindling supplies of medicine, now have to survive the journey out.
Awaiting them outside make shift shelters and a hand to mouth existence for months to come. Hurricane Katrina has killed this city and scattered its people.
Michael Buchanan: Houston, Texas: 1630 GMT
I am at the Astradome Centre in Houston which is serving as the focal point for the city's relief efforts.
We just heard some figures from relief officials here who say they have in this area (Reliant Park) around 19,000 people staying in convention centres and sports stadiums. They say they have capacity to take up to another 33,000-34,000 more people.
In addition to that they say there are a minimum of about 55,000 people living in hotels, churches and garages and private accommodation. They say there are more buses to come. I spoke to a commander who said that this is serving as a central point in Texas for all evacuees.
They are still preparing for up to 10,000 people a day to come through this Houston reception centre.
There is a definite plan here. There are still issues on the ground in terms of people being bussed on. Elderly people will be taken off buses but others will have to travel another four to five hours to Dallas or San Antonio. The plan is for people staying in the Astrodome is to stay for up to four to six weeks. Then they will be sent to more permanent accommodation within Texas or to other cities across the United States.
If people do stay in Texas, the authorities say they will open schools and hospitals for them. And provide some low income housing and try to make it as comfortable as possible for them.
Nobody can give any indication whatsoever as to when people can even go back and have a look at New Orleans let alone go back and rebuild their lives.
Alastair Leithead: New Orleans, Louisiana: 1610 GMT
I have been down to the Convention Centre which is the one place that seems to be ignored for the last few days and since yesterday supplies have started drifting in. Now there is a huge relief effort going on down there. We are hearing reports of the first buses arriving to take people.
This was the most appalling place. People were dying because of a shortage of food. There were shootings, rapes and violence going on. There was no aid or authorities present. People ended up living for days in the rough with no food, no aid and no water.
The aid has been arriving there though. There is a real feeling here that things are starting to turn round. Finally the helicopters that have buzzing around for the last 24 hours really are starting to make a difference.
The troops are restoring law and order at the Convention Centre. They are cleaning up rubbish and are giving out food. They are giving people their dignity back. The people had felt they had been utterly abandoned by their government.
There are a lot of reports of children who are sick. There was an entire old people's home sitting on Convention Centre chairs all night in the dark.
But the aid is starting to come in. It is late, but it is here now.
Daniella Relph: Washington: 1530 GMT
President Bush's weekly radio address is usually a low-key affair that's recorded on a Friday and broadcast on Saturdays.
This was a very different event. Televised live from the White House Rose Garden it was an attempt to reassure America that the Bush administration understood the magnitude of what was happening on the Gulf coast.
President George W. Bush said he had been humbled by what he had seen. He pledged more resources, including the deployment of seven thousand active duty troops in the region.
He also accepted that the government response to this national crisis had not been good enough.
He said he would not rest until he had got this right and got the job done, promising all Americans that the nation had the resources and the resolve to overcome the disaster
Jon Sopel: Gulfport, Mississippi: 1515 GMT
We have seen the Red Cross arriving here. A few blocks from where I am standing, they have set up a centre.
We also had some electricity last night. And about fifteen miles away, we drove to a town where water and electricity had been restored.
And that is going to ease the lives of many of those people effected along the coast here.
There are still tens of thousands of people in need of urgent help.
President Bush spoke about not allowing bureaucracy to get in the way of saving lives.
Dealing with bureaucracy as countries effected by the tsunami in the Indian Ocean found, can be absolutely critical so that the people who need aid most, get it first.
Jon Sopel: Gulfport, Mississippi: 1215 GMT
There are people in the petrol stations just trying to get some fuel to keep their generators running.
You can understand how these people have gone from having had everything to go to absolutely nothing (from first world to third world) overnight. There is a great sense of frustration. There is a great sense of impatience.
I ask people if they can put a number on how many people died and they say no. We have been a few miles down the road and there are splintered bits of wood where houses once stood.
They also do not know how many people were swept out to sea.
People haven't been able to contact others because the phone lines have been down as a guy at a petrol station was trying to tell me.
People don't know where their loved ones are. Phone-ins on local radio stations are heart-rending. People ask - does anyone know this woman? She is my mother. I haven't heard from her. I haven't seen her for four days and if anyone sees her can they call in?
There is a lot of this going on and it's harrowing. For the authorities, they cannot say with any precision what the death toll will be as a result of Hurricane Katrina.
Adam Brookes: New Orleans, Louisiana: 0712 GMT
This evening we have begun to see some measure of relief arrive in places where it is really, really needed.
The convention centre is still dismal, but people there now are getting food and water distributed by troops.
Around 15,000 people are still at the stadium and they too are getting bits and pieces of aid.
This will alleviate the situation slightly but the centre of New Orleans is grim indeed.
New Orleans is a stinking hell hole of a place right now. People are told every day that buses will come and then none turn up.
Once the people are helped out of here, then the clean-up begins and that will take a long time. The water needs to be pumped out.
There will be dead bodies found. Many, many dead bodies will be found everywhere; floating in the streets, in houses, in attics, everywhere.
Then the re-building needs to begin.
In my view the police are not being very helpful and are adding to the alienation by several notches. The police look to me like they have gone really overboard; they are heavily-armed, aggressive, not communicating and they look very, very menacing indeed.
Michael Buchanan: Houston, Texas: 0645 GMT
There was a mild degree of chaos as refugees from New Orleans started to arrive at this sports arena.
The drive took up to 12 hours and then people had to join a very long queue to gain entry.
Everyone had to be frisked to make sure no firearms or weapons were allowed into the stadium.
There was a degree of lack of co-ordination and lack of facilities, but now most people have had food and cleaning facilities.
There are complaints that there is no central point to try to track loved ones, no central phone number or central information gathering point.
There is a great deal of relief among those who have made it, but there is anger at how they were treated while in New Orleans.
There are 15,000 here now and the authorities are expecting up to 200,000 people to arrive here in coming days.
The organisers hope to move people into proper housing within four to six weeks.
They are also hoping to provide counselling for those arriving too, but the main aim is to get people out of these hot, humid conditions and into a better place, into what is being described as more dignified housing.
There is plenty of criticism of President Bush and the federal government in the media here, but talking to these people, they are not blaming the president personally. Many of them tell me that it was an act of nature.
Adam Brookes: New Orleans, Louisiana: 02:51 GMT
The squalid circumstances of the tens of thousands of people stranded in New Orleans were alleviated slightly as military convoys bringing food and water began to arrive. At the Convention Centre, where about 2,000 people have spent six days in atrocious conditions waiting to be evacuated, vast stockpiles of relief supplies appeared.
Troops guarded and distributed bottled water and ration packs. There were other small bright spots in a dismal picture. A hospital, the Medical Centre of Louisiana, was evacuated quickly and efficiently. Thirteen-hundred patients had spent five days without power and with flood water coursing through the corridors.
The federal government and President Bush himself have been on the end of biting public criticism over the tentative early response to Hurricane Katrina. But the new sense of purpose in the air has not defused the anger and frustration on the filthy streets of New Orleans, nor will it dispel a gathering political storm.
Daniel Lak: Gulfport, Mississippi: 00:51 GMT
The United States has never seen an emergency of this scale on its own soil. When humanitarian experts arrive to deal with a catastrophe in a developing country they're usually well equipped to meet people's immediate needs and to get an operation going for the medium and long term.
Here, many of the police and firefighters who first tried to deal with the crisis had themselves been victims. There were no work crews available to clear roads for several days. Bridges and causeways - crucial for travel on this low-lying coast - were all smashed or broken.
Power lines along the coast had been blown down and there were no land or mobile telephone connections. Despite all these obstacles, aid did begin to move in a few days but there was also a problem, say local officials, with the national perception of the scale of this crisis.
The capital, Washington, seemed slow to realise that this would occupy much of the nation's attention for weeks, possibly months to come. Now that President Bush has been here and the media is reporting on almost every detail of relief efforts, it's likely that things will improve here at least.