At the same time, the committee's chairman and its senior Democrat said it is too early to say whether prewar weapons intelligence was manipulated or hyped before the U.S.-led invasion in March, as some Democrats have suggested.
The committee began last week an inquiry into the use of intelligence by President George W. Bush's administration to justify the invasion, specifically assertions that President Saddam Hussein had thriving programs to develop chemical and biological weapons and had tried to obtain material for nuclear arms.
Sen. Chuck Hagel, a Republican, said the administration is cooperating with the committee hearings, and he expects the cooperation to continue.
"This is a cloud hanging over their credibility, their word," said Hagel. "They need to get that dealt with, taken care of, removed."
Hagel, in a televised interview, said: "The world — certainly Americans — must have confidence in this administration. ... And to resolve this issue is certainly in the interests of this administration."
The Intelligence Committee chairman, Sen. Pat Roberts, said he had seen no evidence in the hearings' early going of any manipulation or other questionable administration tactics, but his panel hopes to answer that question once and for all.
"That's why we have all of the voluminous material from the ceiling to the floor from the CIA," the Republican said.
The panel's top Democrat, Sen. Jay Rockefeller, said he does not know whether intelligence may have been exaggerated to bolster the administration's case for going to war, but he added that he has misgivings over the possibility.
Rockefeller pointed to claims that Iraq sought uranium from Africa, which were later determined to be based on forged documents that came to the CIA through Italian and British agencies. Mr. Bush mentioned the purported Niger-Iraq connection in his State of the Union address, apparently after the forgery had been discovered.
For now, Rockefeller said, "I am not going to conclude from that that the president was deliberately misleading."
Their committee held one secret session last week. Roberts said three more hearings are planned, and they probably will be followed by an open hearing, which Democrats have demanded.
"At the end of it, doubtlessly, we will have a public hearing. We'll make a public report and probably a classified report," Roberts said.
The House Intelligence Committee is conducting a similar review on prewar weapons assessments, as is the Senate Armed Services Committee.
More than two months after the fall of Baghdad, no weapons of mass destruction have been found in Iraq, which has raised questions about the Bush administration's primary justification for invading.
Until recently, Mr. Bush and his aides had maintained prohibited weapons would be found. In his radio address Saturday, Mr. Bush made no such promise and said instead that documents and suspected weapons sites were looted and burned "in the regime's final days."