WASHINGTON — Homeland Security Secretary Michael Chertoff acknowledged yesterday that Hurricane Katrina "overwhelmed" the Federal Emergency Management Agency and exposed major flaws in the nation's preparations for terrorism and natural disasters, but contradicted accounts by former FEMA Director Michael Brown about his department's handling of the Aug. 29 storm.

Appearing for the first time before a House panel investigating the government's heavily criticized response, Chertoff vowed to "re-engineer" U.S. preparedness after the storm that killed more than 1,200 people and devastated New Orleans and the Gulf Coast. But he also blamed Brown and FEMA leaders, saying, "We certainly have to fill out the ranks of FEMA in terms of its senior level with experienced staff who can deal with all of the elements" of its mission.

Chertoff rebutted lawmakers' questions about why he worked from home Aug. 27, two days before the Category 4 storm hit, why he made a previously scheduled trip to Atlanta on Aug. 30, and why President Bush stayed at his Texas ranch until Aug. 31. "I don't think there was a sense of a lack of urgency," Chertoff said.

Instead, the secretary expressed growing frustration at days of conflicting reports from the scene, as well as the government's failure to speed relief to thousands of victims at the Superdome in New Orleans or to rescue residents by air or boat.

"I knew I became more involved in operational matters than I would normally expect to be or want to be, given the fact that I had a battlefield commander on the ground," Chertoff said, referring to Brown. "I am not a hurricane expert. I've got to rely on people to execute the details of the plan."

State emergency managers and some critics in Congress say FEMA was crippled after the formerly independent agency was folded into the Homeland Security Department after the Sept. 11, 2001, attacks.

Instead, Chertoff denied Brown's claims, made last month to the House panel, that department budget and personnel cuts led to "the emaciation of FEMA." Chertoff said that from 2001 to 2005, FEMA's "core" budget grew 28 percent, to $447 million, and its staff 19 percent, to 2,445.

With support from department agencies such as the Coast Guard, Chertoff said, "FEMA has better resources and ... it brings more to the table now than it did in the previous five, six, seven years."

If the department fell down, it was "largely in the area of planning" for major catastrophes, he said, which will be consolidated.

Brown testified that he pressed the White House to urge "dysfunctional" Louisiana and New Orleans leaders to order mandatory evacuations earlier before the storm hit. But Chertoff said, "I did not have a problem dealing with state and local officials."

He added: "Let me put it this way: Michael Brown didn't call me. I didn't speak to him prior to Sunday [Aug. 28] and have him tell me that he was having a problem with the governors."

Chertoff said he was unable to reach Brown the day after the storm hit until nearly 8 p.m.

"We now know that [FEMA's] capabilities were overwhelmed by the magnitude of the storm," he said.