WASHINGTON -- A senior U.S. senator on Sunday promised a full investigation into the growing controversy over whether the Bush administration deliberately exaggerated the threat posed by Iraq's chemical and biological arms.

"Under my leadership of the Armed Services Committee and that under Pat Roberts (on the Intelligence Committee) we're going to conduct a very thorough review and investigation," Sen. John Warner said on CNN's "late edition".

"And I guarantee you, this is one senator that holds people accountable when we feel they have strayed from what is right. and I'll guarantee you that'll be done," the Virginia Republican added.

But he said the fact that an investigation was to be held did not imply that the credibility of anyone in the administration was under suspicion.

"I still believe that we should give this administration plenty of time to search them (weapons of mass destruction) out carefully. We've only looked at somewhere between a quarter and a third of the sites," Warner told Reuters.

President George W. Bush and other senior administration figures cited their certain knowledge that Saddam Hussein had stocks of chemical and biological weapons as their main reason for invading Iraq in March.

But so far no such weapons have been found, although Bush has described the discovery of two mobile biological weapons laboratories as vindication of the invasion.

Critics have accused the Bush administration of manipulating intelligence from the CIA and other agencies to fit its agenda and justify its rush to war in Iraq.

Warner expressed confidence in Secretary of State Colin Powell, Defense Secretary Donald Rumsfeld and CIA Director George Tenet.

"These men would not manipulate for political purposes or in any other way that information," Warner told CNN.

Warner also said Tenet had assured him that he would provide Congress with all the statements made by the administration on weapons of mass destruction and the underlying intelligence that supported those statements.