In a letter to CIA Director George Tenet, Republican Sen. Pat Roberts and Democrat Jay Rockefeller, the chairman and vice chairman of the Senate Intelligence Committee, said: "We can be neither complete nor thoughtful, however, without the information we have requested from various elements of the intelligence community."
The inquiry is looking into how intelligence agencies reached their conclusions that Iraq had a nuclear weapons program and chemical and biological weapons. Their prewar findings, used by the Bush administration to make its case for invasion, remain largely invalidated by postwar discoveries in Iraq.
Their letter singled out information requested in July on the intelligence suggesting Iraq had sought uranium from the African country of Niger. That claim, now considered discredited, was part of President Bush's State of the Union address.
"You must expedite our access to the current list of outstanding document and interview requests," the senators say in the letter. "Some of these requests have gone unanswered since July. In light of the agency's many other responsibilities, the committee has been patient, but we now need immediate access to this information."
It set a Friday deadline.
Responding to the letter, a spokesman for Tenet said the CIA and other intelligence agencies are providing volumes of information to the committee.
"The intelligence community is working hard to fulfill the committee's requests and will continue to do so," spokesman Bill Harlow said.
The letter, which Roberts released to the news media, is the latest in a back-and-forth between the committee officials and senior intelligence officials over the inquiry.
CIA officials have defended the analytical process by which they reached their prewar determinations, and said they believe it is too soon to reach any conclusions on whether their findings were accurate, as the hunt for weapons continues in Iraq.
Critics contend the administration mishandled prewar intelligence in making its case for war, but sometimes differ on who is to blame.
Some suggest the intelligence agencies relied on out-of-date or otherwise questionable information to reach its conclusions.
Published reports indicate that the Iraqi defectors who provided key elements of the weapons allegations often inflated their knowledge, and may have unwittingly passed on false information planted by Iraq's intelligence apparatus.
Others say the problem was primarily pro-war members of the Bush administration knowingly distributing marginal intelligence that fit their views, and ignoring contrary information.
Indeed, administration officials often made starker allegations against Iraq than the CIA. The spy agency, for example, warned the White House that it doubted the Niger claim, but the allegation made it into the president's State of the Union speech anyway.
Earlier this month, the head of the search team hunting for weapons of mass destruction said he had seen evidence that Iraq violated United Nations resolutions, maintained the capacity for a biological weapons program and had ambitions to produce chemical and nuclear arms.
David Kay also told Congress Iraq had plans to produce missile that flew beyond U.N.-imposed limits.
But he cited no evidence of actual chemical, biological or nuclear weapons of any active programs to produce them — the heart of the administration's case for war.
Kay's report was only a preliminary set of findings, and the weapons hunt continues, with Kay exploring the possibility that Iraq shipped weapons to Syria before the war, or destroyed them.
But U.S. officials are now considering whether to transfer intelligence experts from the weapons search to the hunt for insurgents who are mounting increasing attacks on American troops.
This week, Mr. Bush defended his decision to go to war.
"Saddam Hussein was in material breach of 1441, which would have been casus belli," the president said Tuesday. "In other words, he had a weapons program, he's disguised a weapons program, he had ambitions."