WASHINGTON (AP) -- Senators want to speak with the former top U.S. weapons inspector who said he couldn't find evidence that Saddam Hussein possessed weapons of mass destruction, a primary justification by President Bush for the war in Iraq.

David Kay, who was scheduled to testify before a Senate committee Wednesday, is one of a number of U.S. officials who have recently adjusted their position on Saddam's weapons capabilities.

As special adviser to CIA Director George Tenet, Kay was chosen last year as the Iraq Survey Group leader in part because he was convinced weapons would be found. "My suspicions are that we'll find in the chemical and biological areas, in fact, I think there may be some surprises coming rather quickly in that area," he said on CNN in June.

Now, Kay says he believes large stocks of weapons are unlikely to be found and blamed faulty intelligence for the misguided assessments.

Kay resigned Friday, saying he was stepping down because resources were being shifted away from the search.

Senate Armed Services Committee Chairman John Warner, R-Va., called the Wednesday hearing to receive Kay's views directly, even though Kay no longer has an official government position.

A U.S. official, speaking on condition of anonymity, said Tuesday that it's premature to speculate about "why we were wrong," and rejected Kay's statement that the work in Iraq is 85 percent done.

"Even if we are 85 percent done, what could you have in that 15 percent of information?" the U.S. official said. "The amount of chemical and biological agent that would be required is extremely small in terms of physical footprint. It could be easily hidden."

While inspectors have been unable to unearth weapons of mass destruction, they have found new evidence that Saddam's regime quietly destroyed some stockpiles of biological and chemical weapons in the mid-1990s, Kay told The Washington Post in an interview in Tuesday editions.

Kay said the evidence consisted of contemporaneous documents and confirmations from interviews with Iraqis and indicated Saddam did make efforts to disarm well before Bush began making the case for war.

Democratic presidential contenders have grabbed onto Kay's conclusion on the absence of banned weapons.

"The administration did cook the books," Howard Dean told reporters Tuesday. "I think that's pretty serious."

Senate Minority Leader Tom Daschle, D-S.D., has called for a new investigation by an independent commission, or a broadened probe by the Senate Intelligence Committee.

Kay's resignation and subsequent statements come as many in the Bush administration subtly are changing their assertions about Iraq's weapons of mass destruction, including President Bush. In last year's State of the Union, Bush called Saddam a "dictator who is assembling the world's most dangerous weapons."

In the State of the Union this month, Bush spoke of Saddam's programs, rather than weapons: "Had we failed to act, the dictator's weapons of mass destruction programs would continue to this day. "

When asked Tuesday by reporters about Kay's assertions, Bush didn't say that the banned weapons would eventually be discovered: "We know from years of intelligence -- not only our own intelligence services, but other intelligence gathering organizations -- that he had weapons -- after all, he used them."

Intelligence officials say the probe will take time, and plenty of work lies ahead. Kay and others have blamed looting immediately after the war on the difficulties in painting a picture. But Kay also has said that flawed intelligence from 1998 forward -- when United Nations inspectors withdrew from Iraq -- contributed to the mistakes.

Last February, Secretary of State Colin Powell told the United Nations Security Council that Iraq possessed weapons of mass destruction that posed "real and present dangers."

"There can be no doubt that Saddam Hussein has biological weapons and the capability to rapidly produce more, many more. And he has the ability to dispense these lethal poisons and diseases in ways that can cause massive death and destruction," he said.

This weekend, Powell began to backpedal, saying the United States thought Saddam had banned weapons, but "we had questions that needed to be answered."

"What was it?" he asked. "One hundred tons, 500 tons or zero tons? Was it so many liters of anthrax, 10 times that amount or nothing?"