President Bush pledged on Thursday to rebuild New Orleans' shattered levee system taller and stronger than before Hurricane Katrina struck, requesting an additional $1.5 billion to buttress the system that failed and left the city flooded. "The federal government is committed to building the best levee system known in the world," said Donald Powell, the top federal official for reconstruction. Officials dodged the question of whether the levees would be built to withstand a Category 5 hurricane, using broader language instead to promise that the city's citizens would be safe and the new levees would exceed anything New Orleans had ever seen. Katrina, a Category 4 storm, surged through the city's levees at numerous points after it hit on Aug. 29, killing 1,300 people in the Gulf region. Louisiana officials have said bringing the levees to Category 5 level is crucial for persuading people to move back. "This action today says come home to New Orleans," Mayor Ray Nagin said after meeting with Bush at the White House. "It's time for you to come back to the Big Easy." Powell said the president already had requested $1.6 billion to repair breeches in the levees, correct design and construction flaws and bring the levee system to a height authorized before the hurricane. This work is to be completed by next June. The additional $1.5 billion the president is requesting would pay to armor the levee system with concrete and stone, close three interior canals and provide state-of-the art pumping systems so that the water would flow out of the canals into Lake Pontchartrain, Powell said. This additional work will take two years. "I'm convinced that what we're doing here today - if there is another Katrina that hits New Orleans that we would not see the catastrophic results that we saw during Katrina," Powell said. "There will be some flooding, but it will be manageable type flooding." In New Orleans, Dan Hitchings, a U.S. Army Corps of Engineers director overseeing levee improvements in the region, said work covered by the new funding likely would still leave areas east and southeast of New Orleans vulnerable to significant flooding if a storm as strong as Katrina hit again. "They would be exposed to the same level of flooding that they were before," Hitchings said, because in those areas, the problem was not levees breaking but rather being swamped by storm surge running well over the top of them. However, Hitchings stressed that the levee system still would be stronger, higher and more modern than it had ever been, leaving the overall risks to the central and western parts of the city, even in the face of another Katrina-size storm, significantly lower. Even if Congress had approved more money for a larger project now, Hitchings said, it would make little difference in the short term. "When you're dealing with 350 miles of levees and floodwalls, it's not physically possible to get all that done by the next hurricane season," he said. "It's not a matter of funding." Later on Capitol Hill, Powell said the government is waiting on a study next year before deciding whether to rebuild the levees to withstand a Category 5 storm. Sen. Mary Landrieu, D-La., called the money "a real step in the right direction." Sen. David Vitter, R-La., said future plans should include a Category 5 design for the most populated areas, adding, "That should engender enormous confidence." Nagin said he was pleased with the announcement. "These levees will be as high as 17 feet in some areas. We've never had that," he said. "These levees will be fortified with rock and concrete. We've never had that before." He also said there would be pumping stations with "backup systems that we only dreamed about." Nagin acknowledged that the most heavily damaged areas of the city - Lakeview and the Lower Ninth Ward - were not ready for returning residents, but he promised they would be eventually. He suggested that officials may need to find residents housing elsewhere in the city in the meantime. The Federal Emergency Management Agency has provided rental assistance to more than 650,000 families so far and is working to bridge that into longer-term assistance programs, said Homeland Security Secretary Michael Chertoff. An estimated 55 million cubic yards of debris have been removed in New Orleans, which is a critical precondition to rebuilding, he said. More than $390 million in community disaster loan assistance has been provided as well as $205 million in unemployment insurance. "In total, the federal government has now provided approximately $5.2 billion in direct assistance to victims of Katrina and Rita," Chertoff said. "So that's a lot of material assistance, but, of course, one of the greatest forms of assistance we can provide people is hope, hope that they can get back to the Gulf Coast and hope that they can get back on with their lives." Bush's announcement came as senators questioned whether local, state or federal officials were responsible for making sure New Orleans levees were in good shape before Katrina hit. A Senate panel investigating the government's response to the storm also released interviews from a federal engineer who described confusion over who should fix the levees in Katrina's aftermath. "Who is in charge?" Army Corps of Engineers Col. Richard P. Wagenaar said in a Nov. 15 interview with congressional investigators, recounting an instance when federal workers attempted to fill in the breached London Avenue canal and were told to stop. "At some point, you know, you've got to make some stuff happen. Because this was a bad situation." Senators at the Homeland Security and Governmental Affairs Committee hearing suggested officials at all levels of government should share in some blame. "All of you didn't do the job that you were supposed to be doing," said Sen. George V. Voinovich, R-Ohio. Also on Capitol Hill, the Senate was working on a package of tax breaks and other assistance that would fulfill Bush's call for a special business zone in the Gulf Coast. Lawmakers hurried to finish the bill before taking a holiday break. The House last week passed its own package of aid worth $7 billion for businesses hurt by Hurricane Katrina.