Mr. Cheney’s vigorous remarks demonstrated his determination to embrace his new role as a fiery defender of the Bush administration policies. But some of his concerns are already reverberating within the Obama administration as officials debate whether the investigation will undercut the work of the C.I.A. or serve as a critical step toward exposing and possibly prosecuting grave acts of wrongdoing that have damaged the nation’s standing abroad.

Officials in the C.I.A. and the Justice Department remain sharply divided about Mr. Holder’s decision to appoint a federal prosecutor to determine if a full criminal investigation into the conduct of agency employees or contractors is needed. On Sunday, it became clear that such concerns were also emerging among some Democrats in Congress.

Senator Dianne Feinstein, the California Democrat who is the chairwoman of the Intelligence Committee, said she remained ambivalent about the wisdom of the inquiry, which will be led by John H. Durham, a prosecutor from Connecticut who has been investigating the C.I.A.’s destruction of interrogation videotapes.

Mrs. Feinstein said she had read the full inspector general’s report. “I was horrified, so I understand the attorney general’s reaction,” she said.

But, speaking on “Face the Nation” on CBS, she warned that “the timing of this is not very good.” She said that her committee was nearing completion of a bipartisan study of interrogation and detention practices and that it should have been allowed to complete its work before a decision was made about an investigation.

Senator John Kerry, the Massachusetts Democrat who leads the Foreign Relations Committee, defended the Obama administration, saying the president had been careful to balance the nation’s national security interests with the need to investigate potential wrongdoing.

In April, Mr. Obama left open the possibility that C.I.A. officers who acted without legal authorization could still face criminal penalties, but he emphasized that those acting on the Justice Department’s legal advice would not be prosecuted, a point Mr. Holder reiterated last week.