Leading members of Congress told Sunday talk shows that they had received voluminous classified materials from US intelligence agencies, which will be reviewed behind closed doors.

"If these weapons are never discovered, it will raise enormous questions about how we put together and act on the intelligence we gather in this country," said Representative Jane Harman, the top Democrat on the House Intelligence Committee.

"And that will make it much harder going forward for this administration or any other administration to claim we should preempt action by some head of a country based on our intelligence," she told "Fox News Sunday>"

US-led forces have yet to locate conclusive evidence backing the US leader's central case for war: that Saddam possessed chemical and biological weapons, pursued nuclear arms, and might one day have armed terrorists with them.

Democrats have pushed for a formal investigation into the intelligence that led the United States to invade Iraq, but President George W. Bush's Republican party has proceedings that would include public hearings.

Senator Pat Roberts, who heads the Select Committee on Intelligence, said he still believes that Saddam possessed banned weapons.

"The real bottom line is what has happened to them, from the standpoint of national security," he told CBS's "Face the Nation."

In an opinion piece Sunday in The Washington Post, Senator John McCain said he was also surprised that US-led forces had not yet uncovered a chemical or nuclear weapons arsenal in Iraq.

"But I find it impossible to credit as serious the suggestion that this war shouldn't have been fought because, lacking better intelligence, we ought to have assumed Hussein's good faith," McCain wrote.

Democrats warned that the reveiw of the intelligence on Iraq could have far-reaching consequences if conclusions about Iraqi weapons programs are not borne out.

"This is not a routine inquiry. This goes to the heart of our intelligence. Is it objective, or has it been shaded -- has it been stretched by the intelligence community to reach some conclusion?" questioned Senator Carl Levin, the top Democrat on the Senate Intelligence Committee.

"The dangers to our future are great if we cannot rely on the intelligence community to give us objective, credible evidence," he told CBS.

Democrats have turned up the heat on the Bush administration, claiming that it exaggerated the threat Saddam posed in order to win public support for the war in Iraq.

With candidates already jockeying to become the Democratic nominee to unseat Bush in 2004, the scant evidence of Saddam's weapons has become a chink in Bush's security policy -- the area considered his strongest point with the public.

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