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The CIA adviser helping lead the search for weapons of mass destruction in Iraq told lawmakers Thursday that the deception that helped nurture Iraq's program won't last for long.

In a closed-door briefing with two Senate panels about the hunt for banned Iraqi weapons systems, David Kay (search), a former chief weapons inspector for the United Nations, said his search team is making new discoveries everyday that help expose "the full extent and nature of Saddam [Hussein]'s program."

Kay said he is building a "solid case" that will withstand international scrutiny.

"We are gaining the cooperation, the active cooperation, of Iraqis who were involved in that program," Kay told reporters after a briefing to the Armed Services Committee. "We are, as we speak, involved in sensitive exploitation of sites that we are being led to by Iraqis. There is solid evidence being produced. We do not intend to expose this evidence until we have full confidence that it is solid proof of what we're proposed to talk about."

Nonetheless, Kay, who has been on the job for a month and a half, asked the senators to be patient.

"We are making solid progress. It's going to take time," he said.

Kay's statements are no doubt welcome at the White House since public confidence in President Bush's handling of Iraq has dropped since the war's end.

According to the latest Fox News-Opinion Dynamics poll, nearly six out of 10 Americans approve of the president's job on Iraq, but that is down 17 percent from the high it reached during the war last April.

Another 59 percent approve of the president's overall job performance, with 31 percent disapproving. That's unchanged over the last two weeks, but down 32 percent since the height of the war.

But lawmakers say Kay's news is good, and they think he is closing in on the proof.

"Don't be surprised if there is a surprise, and it would be very positive," said Senate Intelligence Committee Chairman Pat Roberts, R-Kan., adding that anyone who complains about not having found weapons yet is premature.

"[Saddam] had 20 years and 10,000 Iraqis and billions of dollars in a program of denial and deception. We've had six weeks," Roberts said.

Kay said Iraqi scientists and newly-found documents have led the search team to previously unknown sites. He did not dispute reports that his team still hasn't found any chemical or biological weapons. He said the old regime in Iraq undertook extreme methods to hide its weapons program.

"The active deception program is truly amazing once you get inside it. We have people who participated in deceiving U.N. inspectors now telling us how they did it," Kay said.

Sources say Kay's goal is to build an understandable and indisputable case even without a smoking gun. But critical Democrats say Kay must do more to find stocks of chemical and biological weapons and convince them that the stockpiles presented an urgent threat.

"If we do not find that they were positioned in a way for imminent use, the credibility of the United States government abroad and the credibility of the United States government with its own people here in the United States will be significantly eroded," said Florida Sen. Bob Graham, former chairman of the Senate Intelligence Committee and a Democratic presidential aspirant.

Kay told reporters that he doesn't know what a smoking gun is, but he made clear that he does understand credibility.

"We have said we will not come forward with evidence until we satisfy three criteria — multiple Iraqis willing to talk and explain the program, documentary evidence and more than one document that explains what we're after, and physical evidence associated with a program," he said. "We do not want to go forward with partial information that we have to retract afterwards."

Kay spoke a day after the president defended his own credibility by taking personal responsibility for his State of the Union address claim that Iraq sought nuclear material in Africa.

A few hours, later National Security Adviser Condoleezza Rice, who at first blamed the CIA for the now-discredited claim, said now it was her fault.

"I feel personal responsibility for this entire episode," she said.

However, Bush may find the public is willing to forgive him about the disputed weapons claims even if congressional Democrats are not. Of those surveyed in the Fox News-Opinion Dynamics poll, only 12 percent said finding weapons of mass destruction was the top priority of the U.S. in Iraq. The largest majority, 41 percent, said establishing a government is the most important goal, while 25 percent said finding Saddam is the top priority.

Fox News' Wendell Goler and James Rosen contributed to this report.