WASHINGTON – Homeland Security Secretary Michael Chertoff on Monday rejected accusations that he had neglected preparedness for natural disasters because he was preoccupied with terrorism, but he likely will face tough questioning today from the Senate about his role in the government’s flawed response to Hurricane Katrina.

“I want to tell you, I unequivocally and strongly reject this attempt to drive a wedge between our concerns about terrorism and our concerns about natural disasters,” Chertoff said in a speech to emergency response managers, declaring that he had always considered dealing with natural disasters a central part of his mission.

The secretary is expected to be pressed hard, however, by Republicans as well as Democrats when he appears before the Senate Homeland Security and Governmental Affairs Committee today. The panel is investigating what went wrong in the response to Katrina.

Although the Bush administration has maintained that the magnitude of the storm took federal officials by surprise and overwhelmed their response plans, Senate investigators have documented a stream of advance warnings and internal communications that spelled out in graphic detail what Katrina would do to New Orleans and the Gulf Coast.

In one example obtained from Senate investigators, the transcript of a conference call hours before the storm hit shows that Chertoff and President Bush were told by Max Mayfield, head of the National Hurricane Center, that “the greatest potential for large loss of life is … in the coastal areas from the storm surge.”

Other warnings that circulated widely through the Homeland Security Department and the Federal Emergency Management Agency predicted that levees protecting New Orleans would fail and that huge areas of the city would be flooded for weeks or months to come.

Chertoff also Monday outlined plans to improve and streamline his department’s systems for dealing with disasters, including improved communications and the creation of a permanent, full-time unit – numbering as many as 1,500 new federal workers – who would be prepared to take the lead in any future emergency.

The Katrina debate was further fueled Monday by testimony before the Senate committee that chronicled what one senator called an “infuriating” catalog of wrongdoing in the dispersal of $85 billion in federal aid.

The government’s effort to rush money and aid to stranded Americans resulted in gargantuan fraud, the witnesses said, including victims receiving duplicate $2,000 debit cards, scam artists making money off fraudulent charitable Web sites, and FEMA officials ordering 25,000 wide-bodied trailers that investigators say will now have to be sold for “pennies on the dollar.”

Of the 2.5 million applicants who received various emergency assistance from FEMA, up to 900,000 were fraudulent, witnesses said.

The testimony was given by officials from the Justice Department, the Homeland Security department’s inspector general’s office and the Government Accountability Office, an arm of Congress.

Meanwhile, about 12,000 families made homeless by last year’s hurricanes began checking out of their federally funded hotel rooms around the country Monday after a federal judge let FEMA stop paying directly for their stays.

FEMA promised evacuees that they will still receive federal rent assistance that they can put toward hotel stays or other housing. But the agency will no longer pay for their hotel rooms directly.

Earlier in the day, attorneys for the evacuees pleaded with U.S. District Judge Stanwood Duval for a last-minute reprieve, saying the rent assistance will not be enough for decent living accommodations or continued hotel stays. But Duval denied the request.

FEMA said the majority of those checking out had made arrangements for other housing. But some said they had nowhere to go except their own cars, a relative’s couch or back to a shelter.