Mr Bush took “full responsibility” for Washington’s botched response to Katrina a year ago and pledged to be better prepared for future hurricanes.
"This anniversary is not an end. And so I've come back to say that we will stand with the people of southern Louisiana and southern Mississippi until the job is done," Mr Bush said.
Mr Bush also pleaded with residents who fled the storm and did not return to New Orleans, by saying: "The people of this city have a responsibility as well. I know you love New Orleans. And New Orleans needs you. She needs people coming home."
He predicted that the festive city known as the “Big Easy” would someday be "louder, brasher and better."
Tears and Anger
As is traditional in New Orleans a somber jazz funeral procession was one of the ways the city marked the first anniversary of Hurricane Katrina.
The tears were mixed with anger at officials who abandoned tens of thousands to the chaos and whose bureaucratic bungling continue to complicate reconstruction efforts.
But many tried to push their frustrations aside for the day and focus on remembering those who died and bringing back the spirit of the jazz capital.
"We're here on a very solemn occasion," Mayor Ray Nagin said at a ceremony in front of city hall, which still bears the scars of Katrina's wrath.
"We're here to commemorate what happened and to think about that particular moment when the suffering started," he said before ringing a bell to mark the moment when the first levee was breached at 9:38 am.
"There are lots of New Orleanians who are suffering today," Mr Nagin said. "I am personally having a difficult time with it. But trust me that we will get through it."
President Bush’s promises mean little to those still waiting for help a year after Katrina ravaged the Gulf Coast on August 29, 2005 and killed more than 1,500 people.
"The little bit they're giving us is like giving scraps to a dog," said Germaine Bush, who joined a march demanding the "right to return" for the thousands of people made homeless when 80 percent of the city was flooded.
Huge swaths of the city remain abandoned to rot and ruin. More than 200,000 people are still scattered across the country, and those who have returned are still waiting for government funds to help repair their homes.
Devastation remains
New Orleans didn’t suffer the brunt of Hurricane Katrina but the storm surge put a strain on the city’s industrial canal and levee system.
Under the pressure levees burst and rushing floodwaters swallowed 80 percent of the city, reaching depths of six meters in some areas. The bulk of the storm's deaths were in those flooded neighborhoods.
In the days after the hurricane the rest of America watched in shock, images of survivors begging to be rescued from rooftops or freeway overpasses. Forty-nine bodies remain unidentified in the city's morgue.
Throughout the city, white trailers still line driveways in neighbourhoods where debris is stacked up in piles and unchecked weeds have overtaken abandoned houses. Only half the population has returned.
Emergency medical care is doled out in an abandoned department store, while six of New Orleans' nine hospitals remain closed. Only 54 of 128 public schools are expected to open this autumn.