Senate Intelligence Committee chairman Pat Roberts said questions about U.S. intelligence will instead be examined in closed door hearings beginning next week.
"We're going to complete a very thorough review of all the documentation," said Roberts, a Kansas Republican.
Leading Senate Democrats want an investigation into the question of whether intelligence on weapons programs was inaccurate or manipulated to make the case for war.
In arguing for a public probe, some Democrats say the credibility of U.S. intelligence is at stake because of the failure to locate weapons of mass destruction and problems in some of the evidence cited by the administration. Documents indicating Iraq imported uranium from Niger turned out to be forgeries. Aluminum tubes described as intended for nuclear weapons were probably meant for conventional artillery rockets.
Hours after Senate Republicans made their decision against a public probe, a report surfaced indicating that the CIA - long before the war - had information disputing a claim President Bush used in his State of the Union speech last January, as proof of Iraq having an active nuclear weapons program.
At that time, Mr. Bush said that Iraq had tried to buy uranium from Niger. But according to senior administration officials and a former government official quoted in Thursday's Washington Post, a CIA-directed mission to Niger in early 2002 had already disputed the claim about Iraq and Niger.
The newspaper says the CIA did not, however, pass on to the White House its doubts about the Niger uranium claim, an omission a senior intelligence official blames on "extremely sloppy" work.
That same official told the Post that "It is only one fact and not the reason we went to war. There was a lot more."
A senior CIA analyst interviewed by the newspaper says what happened with the uranium claim is "indicative of larger problems." He furthermore charges that "information not consistent with the administration agenda was discarded and information that was [consistent] was not seriously scrutinized."
Skeptics of the Bush administration's pre-war collection and handling of information about what weapons Iraq might and might not have had gained a little more ammunition Wednesday.
CBS News Chief White House Correspondent John Roberts reports that in an interview with Britain's Guardian newspaper, the U.N.'s chief weapons inspector, Hans Blix, railed against U.S. officials he said had tried to undermine his team's work in Iraq.
Blix said some U.S. officials waged a "smear campaign" to discredit him, since no banned weapons have been found in Iraq. And he said the Bush administration "leaned" on his team in the days before launching the war in Iraq.
"There are bastards who spread things around, of course, who planted nasty things in the media. Not that I cared very much," said Blix.
Sensing that the Pentagon's hunt for weapons is going nowhere, the White House said Wednesday it was hiring former weapons inspector David Kay as a special advisor to the new search team.
At the same time, Republicans dismissed as "pure politics" charges the administration "hyped" the intelligence on Iraqi weapons.
Roberts, R-Kan., said some of the Democratic criticism of the handling of the intelligence has "been simply politics and for political gain."
"I will not allow the committee to be politicized or to be used as an unwitting tool for any political strategist," Roberts said.
Democrats, for their part, claim that the White House is pressuring the committee chairs to "put out the fire" on the weapons issue - at a time when the stakes are very high for the U.S.
"We have to be able to rely on our own intelligence," said Sen. Carl Levin, D-Mich., ranking member of the Armed Services Committee. "The world has to be able to rely on our word," Levin said.
The political stakes of any investigation could be high before next year's election if President Bush's primary reason for going to war continues to be called into question. Roberts and other GOP senators said the White House did not attempt to influence their decisions on an investigation.
In fact, White House press secretary Ari Fleischer, traveling with Mr. Bush for a presidential speech in Chicago, said the administration "welcomes the review."
"We always work together with Congress on dealing with the threat of Iraqi possession of WMD," he said. "And we'll continue to work with Congress on the facts that led previous administrations, Democrats and Republicans alike, to know he (Saddam) had WMD."
"This is an important part of Congress' oversight and we welcome it," Fleischer said.
Roberts said his committee will evaluate prewar intelligence on Iraq's weapons of mass destruction and its connection to terrorist groups. It will examine whether the findings were reasonable and accurate. The CIA has begun submitting details of the intelligence that supported administration claims on Iraq's weapons programs.
Roberts added that "when the committee deems it appropriate, we will make whatever public statements that are necessary." The Senate Armed Services Committee has already begun closed-door hearings on the intelligence issue.