He said in the speech delivered from Jackson Square in the heart of the French Quarter in New Orleans, "[W]e will stay as long as it takes, to help citizens rebuild their communities and their lives."
"And all who question the future of the Crescent City need to know: There is no way to imagine America without New Orleans, and this great city will rise again."
President Bush unveiled a massive rebuilding program for New Orleans and other parts of Louisiana, Mississippi and Alabama that he is calling "one of the largest reconstruction efforts the world has ever seen."
"Federal funds will cover the great majority of the costs of repairing public infrastructure in the disaster zone, from roads and bridges to schools and water systems," he said. "Our goal is to get the work done quickly. And taxpayers expect this work to be done honestly and wisely -- so we will have a team of inspector generals reviewing all expenditures."
He said the federal government is providing immediate assistance to those displaced by the hurricane, and that they could expect even more financial support in the future. At least 800 people died from the Aug. 29 storm, mostly in Louisiana and Mississippi, and more than 1 million people have been displaced.
The government is sending extra doctors and nurses to storm-ravaged areas and providing temporary housing for personnel servicing and rebuilding the region, he said.
As for tackling longer-term problems, the president said Hurricane Katrina revealed a persistent poverty problem with "roots in a history of racial discrimination." When the areas are rebuilt, he said, there should be more minority-owned businesses, homeowners and jobs.
"We have a duty to confront this poverty with bold action," he added.
President Bush also acknowledged Thursday that the different levels of government were not well-coordinated for such a massive natural disaster and were overwhelmed in the first few days.
"Four years after the frightening experience of September 11th, Americans have every right to expect a more effective response in a time of emergency. When the federal government fails to meet such an obligation, I, as president, am responsible for the problem, and for the solution," he said.
The president and the Senate Homeland Security and Governmental Affairs Committee have launched separate investigations into the federal response. Mr. Bush said Thursday that he is directing the Department of Homeland Security to review emergency plans in every major city in America.
The speech marked the fourth time the president has visited the flood-ravaged Gulf Coast.
In the wake of the hurricane, the president has seen his lowest approval ratings -- about 40 percent -- since he took office nearly five years ago.
Two weeks after the hurricane made landfall, the head of the Federal Emergency Management Agency, Michael Brown, resigned amid intense criticism, saying he wanted the focus to be on FEMA's recovery efforts.
Earlier Thursday, New Orleans Mayor Ray Nagin said residents could start returning over the weekend to large areas of New Orleans, starting with Algiers, across the Mississippi River from the French Quarter.
The New Orleans suburbs of Gretna, Westwego and Lafitte in Jefferson Parish started allowing residents to return to inspect their damaged homes on Wednesday.
Louisiana Gov. Kathleen Blanco, who has repeatedly blasted the federal response as too slow, pledged Wednesday in front of a joint session of the state legislature in Baton Rouge to rebuild New Orleans and other damaged areas of her state to allow more than 1 million displaced residents to return home, reported CNN.
"As your governor, I pledge that I will not rest until every Louisiana family and community is reunited," Blanco said in a televised address before a joint session of the state Legislature in Baton Rouge.
"I want the world to know what we know: We are brave, we are resilient, and we will prevail."
Blanco, a first-term Democrat from Lafayette who has been in office less than two years, conceded "there were failures at every level of government, state, federal and local," in the response to the disaster.
"At the state level, we must take a careful look at what went wrong and make sure it never happens again," she said. "The buck stops here, and as your governor, I take full responsibility."