The former head of the U.S. Federal Emergency Management Agency has defended his record in responding to Hurricane Katrina. Michael Brown faced tough questioning before a Republican-led House of Representatives committee, one of two congressional inquiries under way into federal, state and local responses to the storm.

Michael Brown was relieved of his duties managing the aftermath of Hurricane Katrina amid sharp criticism of his performance, and later resigned his position as head of the Federal Emergency Management Agency (FEMA).

In testimony, he said FEMA, among a range of other actions, had pre-positioned disaster supplies, equipment and manpower to be moved into the hurricane zone once it was safe to do so:

"I want this committee to know that FEMA pushed forward with everything that it had, every team, every asset that we had, in order to help what we saw as being a potentially catastrophic disaster," he said. "FEMA was prepared to fulfill its role as a partner in responding."

Mr. Brown asserts FEMA used exactly the same procedures responding to Katrina as it did in other natural disasters, from hurricanes and earthquakes to forest fires.

But he says the agency had what he called great difficulty establishing a unified command structure in the state of Louisiana, and aimed this criticism at local and state leaders:

"I very strongly, personally, regret that I was unable to persuade [Louisiana] Governor Blanco, and [New Orleans] Mayor Nagin, to sit down, get over their differences, and work together," he said. "I just couldn't pull that off."

Saying his biggest mistake was not recognizing earlier that "Louisiana was dysfunctional, Mr. Brown said he should have pushed harder to overcome what he called the reticence of the state's officials to order an immediate evacuation.

His comments provoked sharp and often angry responses from Democratic lawmakers representing hurricane-hit areas of the Gulf Coast, such as Congressman William Jefferson.

"I find it absolutely stunning that this hearing would start out with you, Mr. Brown, laying the blame for FEMA's failings at the feet of the governor of Louisiana and the mayor of New Orleans," he said.

Mississippi Congressman Gene Taylor asserted the agency failed to plan adequately for emergency communications and evacuation, as well as needs for emergency food and fuel supplies.

"You can try to throw as much as you can on the backs of [people from Louisiana], but I am a witness as to what happened in Mississippi," he said. "You folks fell on your face. You get a F-minus [failing grade] in my book."

Congressmen Taylor and Jefferson are two of only three Democrats who accepted an invitation from Republicans to participate in the committee.

Lawmakers continue to argue over the method for investigating the hurricane response, with House Democrats renewing their call for an independent commission.

One Republican, Congressman David Dreier, pointed to tough questioning of Mr. Brown as proof the Republican-led panel is doing its job.

"The Democratic leader said these hearings would be nothing but a white-wash," he said. "Well having seen the questions raised by my Republican colleagues on the committee, they are tough, strong, hard questions that are being raised of the former FEMA administrator Mr. Brown."

However, Democrats announced they will use a special legislative procedure known as a "discharge petition" to force debate and a possible vote on a Democrat-backed resolution demanding creation of an independent commission.