The White House has refused to allow the interrogation of top administration officials and advisers to President Bush citing executive confidentiality privileges and has said it would not turn over all documents relating to the disaster response until it has completed its own investigation.
"The problems begin at the White House, where there has been a near total lack of cooperation that has made it impossible, in my opinion, for us to do the thorough investigation we have a responsibility to do," said Senate Governmental Affairs Committee ranking Democrat Sen. Joseph Lieberman, Conn., Reuters reported.
But Lieberman and the committee's chairwoman, Republican Susan Collins of Maine, said other agency officials have been advised not to speak to the committee.
"We are entitled to know if someone from the Department of Homeland Security calls someone at the White House during this whole crisis period," Collins said. "So I think the White House has gone too far in restricting basic information about who called whom on what day."
Collins and Lieberman did not say whether they would subpoena officials, the Associated Press reported.
Two congressional committees have opened investigations into the disaster response, the Senate committee and the House Select Bipartisan Committee to Investigate the Preparation for and Response to Hurricane Katrina.
Prior to the committees' formation, Democrats had called for an independent commission to investigate the response, but the measure failed.
White House spokesman Trent Duffy said the administration has cooperated with both inquiries.
"There is a deliberate process, and the White House has always said it wants to cooperate with the committee but preserve any president's ability to get advice from advisers on a confidential basis," Duffy said, according to the AP. "And that's a critical need for any U.S. president, and that is continuing to influence how we cooperate with the committees."
Duffy and officials from the departments of Defense and Homeland Security said the committees already have questioned several officials -- 75 from the Defense Department alone -- and that the department had provided an estimated 240,000 pages of documents, the New York Times reported.
The House and Senate committees are scheduled to conclude their investigations, which began in September after Katrina slammed the Gulf Coast, by Feb. 15 and mid-March respectively.
The committees have questioned about 260 witnesses from local, state and federal governments and from the private sector, according to the AP. They have received an estimated 500,000 documents for review.
Senate committee hearings since the start of the investigation have included testimony from David Paulison, the federal Emergency Management Agency's acting director, and testimony from various officials on levee construction and Coast Guard response during the storm.