The acting head of the US emergencies agency has pledged to do more to help the Hurricane Katrina survivors currently living in relief shelters.
Tens of thousands are living in temporary relief shelters
"We're going to get people out of the shelters, we're going to move on and get them the help they need," R David Paulison told reporters.
Mr Paulison took over at the Federal Emergency Management Agency after chief Michael Brown stood down on Monday.
President Bush said responsibility for any mistakes ultimately lay with him.
"Katrina exposed serious problems in our response capability at all levels of government, and to the extent that the federal government didn't fully do its job right, I take responsibility," Mr Bush said at a news conference.
"I want to know what went right and what went wrong."
Both Mr Bush and Mr Brown have faced severe criticism for federal government's handling of the disaster.
Mr Bush will address the issue in a major speech to the US people on Thursday, the White House has announced.
In his first public comments since taking the reins of Fema, Mr Paulison said he had been busy "getting brought up to speed" on the relief effort.
He said that he had spoken to the president who had promised he would have "the full support of the federal government".
Meanwhile, the bodies of 45 dead patients have been found in a New Orleans hospital, as the task of recovering the dead continued.
The grim find at the Memorial Medical Center is the biggest discovery of bodies so far.
How the patients died is unclear. One hospital official said the heat after the storm was a factor, while another said some were already dead.
Hospital administrator Dave Goodson told the BBC News website he was "disappointed" by a lack of co-ordination in official efforts to evacuate the 317-bed facility.
Staff made heroic efforts to care for the patients who remained in the days after the storm, he said. But heat played "a major factor" in the deaths.
However a spokesman for the hospital's owner, Tenet Healthcare Corp, told the Associated Press some patients were dead before the storm arrived.
None of the deaths resulted from a lack of food, water or electricity to power equipment, Steven Campanini said. Many of the patients were seriously ill.
A house-by-house search for the dead continues in New Orleans and elsewhere. The overall confirmed death toll in the hurricane-affected states is now above 500.
Officials have said the final number of dead could be much lower than the thousands feared initially.
Emergency crews are now reaching outlying areas of Louisiana and Mississippi, as well as the New Orleans neighbourhoods worst hit by flooding.
The BBC's Daniel Lak in New Orleans says the sight of receding waters is starting to tempt a few residents back, despite warnings from the authorities over the health risks.
The city's airport is due to re-open for commercial flights on Tuesday, in a small sign of progress.