WASHINGTON — Homeland Security Secretary Michael Chertoff said today the Federal Emergency Management Agency was overwhelmed by Hurricane Katrina and must be retooled to improve preparation and response to natural disasters like the one that swamped the Gulf Coast.

"There are many things that did not work well with the response," Chertoff said in written testimony to a House panel investigating the federal response to Katrina.

"We are not where we need to be as a nation in the area of preparedness," he acknowledged.

Chertoff's appearance came as weather forecasters kept a wary eye on Hurricane Wilma, the latest in a host of such storms, as it has grown into one of the most intense Atlantic hurricanes on record. Forecasters said it likely will strike the east coast of Florida with devastating winds by late in the week.

Most of the blame for the federal response to Katrina has fallen on former FEMA Director Michael Brown, who resigned last month after Chertoff removed him from direct responsibility for Katrina relief and recovery efforts.

Brown appeared before the House panel last month and blamed state and local officials in Louisiana and the White House for the dismal response to the hurricane, which killed more than 1,200 people, flooded New Orleans and forced the evacuation of hundreds of thousands.

Today's hearing provided the first opportunity for lawmakers to question Chertoff directly about his role in the response. FEMA was an independent agency before it was folded into the Department of Homeland Security when it was created after the Sept. 11 terrorist attacks.

The investigation is being conducted by a special committee appointed by House GOP leaders. Democrats, insisting on an independent investigation, have refused to cooperate in what they contend is a too-soft probe of the Bush administration by GOP lawmakers. Several Democratic congressmen from the affected areas have attended the hearings and questioned witnesses, however.

Chertoff said Katrina demonstrated that FEMA's system for moving supplies into disaster areas is not adequate and that communications systems must be made to work even in the worst disasters. He said the agency also must learn how to identify issues and target resources when state and local officials are overwhelmed by a storm.