After days of criticism over the federal response to Hurricane Katrina, U.S. President George Bush announced Tuesday he is going to oversee an investigation into what went wrong.

Bush said he wants to make sure that the United States is ready for future storms or attacks.

"Bureaucracy is not going to stand in the way of getting the job done for the people,'' the president said after a meeting at the White House with his cabinet.

Bush visited Baton Rouge and Poplarville, Miss., on Monday during his second ground tour of affected areas. He is sending Vice-President Dick Cheney to the Gulf Coast region on Thursday to see if the government is doing all it can.

Defense Secretary Donald Rumsfeld told reporters Tuesday that state and local officials are constitutionally responsible for first response in disaster situations.

"And (then) you have a disaster of this magnitude where the first responders are incapable of functioning, given the seriousness of it," he said, noting many first responders' families were themselves victims.

The defence department and military are attempting to adjust to changing circumstances as quickly as possible, he said.

Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said there are currently 41,000 National Guard and 17,000 active-duty personnel in the hurricane zone.

He said the military had started gearing up for the response before Katrina struck.

Meanwhile, authorities are reporting some progress in New Orleans, after a gap was closed in the floodwalls that burst following Hurricane Katrina, flooding 80 per cent of the city.

The U.S. Army Corps of Engineers is now pumping the flood waters that devastated the bowl-shaped city back into Lake Pontchartrain. They are also working to plug another major breach.

However, it will likely take three weeks to remove the water, and up to eight weeks to get electricity back on, New Orleans Mayor Ray Nagin told NBC's "Today" Show.

"I've gone from anger to despair to seeing us turn the corner," he said.

Once the pumping is done, officials expect to find a layer of sludge and toxic waste -- as well as countless bodies. Nagin has said a death toll of 10,000 "wouldn't be unreasonable."

The mayor of the hard-hit city is trying to convince stragglers to evacuate, saying gas is leaking, and there is no running water.

Nagin said the city has the authority to force residents to evacuate. He did not detail exactly how that would be done, but did say that water would no longer be handed out to people who refuse to leave.

People displaced by Katrina will get debit cards to pay for necessary personal items, according to the U.S. government.

Katrina's star power

Some big names were out over the weekend to lend their support to the tens of thousands of hurricane victims.

Former U.S. president Bill Clinton and Bush's father, George Bush Sr., visited evacuees in the Astrodome complex in Houston. They are heading up a fund-raising effort for victims of Katrina.

Talk show diva Oprah Winfrey and Rev. Jesse Jackson were also at the Astrodome Monday to listen to the complaints of the thousands left homeless by the storm. Oprah will host a live show from the Astrodome today.

Also on hand on Monday was movie star couple John Travolta and Kelly Preston, who flew their own jet loaded with supplies to New Orleans. They met with Jefferson Parish Sheriff Harry Lee.

Actor Sean Penn helped rescue several people in New Orleans by chartering his own personal boat, according to The New York Daily Times. Other reports suggested he had to abandon his efforts when his boat began to take on water.

In addition, several celebrities have donated money, including writer John Grisham and pop star Celine Dion.

Some of the world's poorest countries, including Bangladesh, Afghanistan and tsunami-hit Indonesia, have also offered financial aid and personnel.

In Canada, Prime Minister Paul Martin was in Halifax on Tuesday to see off 1,000 military personnel and four ships headed for Louisiana.

The ships will carry more emergency supplies to the U.S. Gulf Coast. A planeload of medical supplies from Canada arrived Sunday in Atlanta for distribution to areas of need.

In related news:

• U.S. oil prices fell on Tuesday amid reports that half of the Gulf Coast oil refineries damaged by the hurricane plan to begin the process of restarting production this week
• Residents of suburban Jefferson Parish near New Orleans were allowed to take their first look at Katrina's damage to their homes on Monday
• Former U.S. first lady Barbara Bush was quoted as saying that many of the people at the Astrodome were: "underprivileged anyway."