As Kay returns Thursday, any reports of breakthrough would come as a surprise.
Kay, the CIA's special adviser for the weapons search, begins two days of closed-door meetings in Congress, and lawmakers don't expect him to announce any major discoveries.
Some are becoming increasingly skeptical that search teams will ever uncover weapons that were a primary reason cited by the United States to topple Saddam Hussein's regime.
"There don't seem to be signs of it at this point," said Sen. Jay Rockefeller of West Virginia, the top Democrat on the Senate Intelligence Committee. "There is nothing that would lead me to believe that it (a discovery) is imminent."
Of Kay's appearance, he said, "I don't think he's going to have a lot to tell us."
Prime Minister Tony Blair, however, said Kay's interim report on the search for weapons could hold some surprises.
"I think people may find that some of the speculation and the leaks fall way short of what the report actually says," Blair told Britain's independent television network ITV.
In a related development, the New York Times reports that the Bush administration is seeking an additional $600 million to fund the search for weapons of mass destruction.
The newspaper said the new money the White House is seeking from Congress is in addition to about $300 million already spent on the WMD search.
On Wednesday, Washington Post reported that weapons hunters were exploring the possibility that Saddam Hussein was bluffing for years about his weapons of mass destruction capabilities in order to deter invasion and deceive his own people.
The newspaper said Kay may discuss the possibility that Saddam was bluffing in his briefings to the House and Senate intelligence panels
Kay's interim report to Congress, which the CIA insists is only preliminary, has been widely anticipated.
Iraq's alleged chemical and biological weapons and suspected ongoing nuclear program were the main justification for the U.S.-led war, but no evidence has been reported of weapons stockpiles or an active nuclear program.
Indications are Kay's report will offer no new evidence that such weapons existed but will not rule out the possibility of them turning up later.
According to The Post, Kay is expected to report that Saddam retained the ability to make chemical and biological weapons and planned to seek nuclear arms if sanctions were lifted. He is expected to say that after United Nations inspectors left in 1998, Saddam bought equipment that could be used to make banned arms.
One theory is that Saddam kept "starter kits" on hand that could have been used to quickly restart programs to produce weapons of mass destruction. In addition, the newspaper reports Kay has new evidence Iraq was trying to build rockets to violate a U.N. range limit.
But war critics will seize on the key distinction between the ability to make weapons of mass destruction and the U.S. allegation that Iraq already possessed or was actively manufacturing those weapons. They will also point to the implication that sanctions were restraining Saddam's ambitions.
Kay will also, according to The Post, detail Saddam's long-suspected deception of U.N. inspectors, an effort that included hiding documents and materials, recording interviews with Iraqi scientists that were supposed to be secret and barring those scientists from leaving the country.