The storm killed 1,900 people, more than 1,500 in New Orleans, where Mr Bush made his comments on the anniversary of the worst natural disaster in US history. The delayed rescue efforts at the time shocked America.
Mr Bush admitted today that the "hurricane brought terrible scenes that we thought we would never see in America". He also conceded that the government "fell short" at "all levels".
"I take full responsibility for the federal government's response."
But he insisted that lessons had been learned and he promised more aid to New Orleans and the wider area.
"The debris is getting clear," he said. "I simply could not imagine an America without the crescent city."
Mr Bush also paid tribute to the rescue efforts that were made. "People looked up to the skies for deliverance, and then they saw the choppers come."
Earlier today, Mr Bush met the New Orleans mayor, Ray Nagin, and attended a service at St Louis cathedral in the French Quarter.
In the aftermath of the disaster, the president stood by the cathedral and admitted that his administration had failed to respond adequately.
The White House hopes regeneration of the Gulf Coast will erase the damage done to Mr Bush by the sluggish official reaction to the storm. Earlier this month, an AP-Ipsos poll revealed that 67% of Americans disapproved of his handling of the disaster.
Officials said the purpose of Mr Bush's trip was not to dwell on the disaster but to highlight rebuilding efforts, thank volunteers and celebrate community spirit.
However, frustration at the state, local and federal response in New Orleans - which still has no master rebuilding plan - remains intense. Only 50% of the city has electricity, half of its hospitals remain closed and violent crime has risen.
Less than half the population has returned since the storm, with tens of thousands of families living in trailers and mobile homes, and insurance settlements mired in red tape.
Last year, Mr Bush promised to help fight poverty in the area. Proposals included the Gulf Opportunity Zone, which would give more than £5bn in tax breaks to developers of low-income housing, small businesses and individuals.
However, worker recovery accounts - which were meant to help storm victims find work by paying for school, job training and childcare - did not materialise. Neither did the Urban Homesteading Act, which had been intended to provide the poor with sites on which to build self-financed homes.
