NEW ORLEANS — Vowing that this waterlogged virtual ghost town will rise again, President Bush pledged on Thursday night an unprecedented federal response to Hurricane Katrina that he said should include tax breaks for businesses, help for the displaced poor and revamped evacuation plans for the future.

In a nationally televised address from the historic French Quarter, Bush sought to reassure Americans and especially the victims of Hurricane Katrina, many of whom criticized the initial rescue efforts, that Washington will be bold in the recovery job.

"We will do what it takes. We will stay as long as it takes to help citizens rebuild their communities and their lives," he said. "There is no way to imagine America without New Orleans, and this great city will rise again."

The president said that federal funds would cover the great majority of the costs of repairing infrastructure, including roads, bridges, schools and water systems. He called the undertaking "one of the largest reconstruction efforts the world has ever seen."

Bush, however, provided no cost estimate for the endeavor. Congress has already approved $62 billion, making Katrina the most expensive natural disaster in U.S. history. Total expenses could reach $200 billion, Senate Budget Committee Chairman Judd Gregg, R-N.H., told the Wall Street Journal last week, a figure that would rival the total spent so far on the Iraq war.

Bush acknowledged that the emergency response to the devastation from the hurricane was disorganized and that responders were overwhelmed. His speech, delivered from Jackson Square, a popular tourist destination next to the Mississippi River, comes as national polls show public approval of his job performance reaching new lows and ratings for his leadership ability, once considered the president's strong point, also dropping.

A CBS/New York Times poll released Thursday showed 51 percent of Americans are uneasy with Bush's ability to make decisions about the hurricane. Forty-six percent expressed confidence in his ability.

Most of the New Orleans residents who were stranded in the horrific aftermath of the storm are black, and on Thursday night the president noted that the hurricane has exposed poverty in the Gulf Coast region.

"That poverty has roots in a history of racial discrimination, which cut off generations from the opportunity of America . . . ," he said. "So let us restore all that we have cherished from yesterday and let us rise above the legacy of inequality."

To remedy the problems, Bush offered some of the "compassionate conservative" agenda that he stressed during his first presidential campaign but which has lately been overshadowed by the war in Iraq and other White House priorities such as the use of private retirement accounts under Social Security.