WASHINGTON -- Chief U.S. weapons searcher David Kay reported Thursday he has uncovered no weapons of mass destruction in Iraq, and only limited evidence of secret programs to develop weapons, drawing fresh congressional complaints about the Bush administration's prewar assertions of a serious threat from Saddam Hussein.

Kay, in a report to Congress, described evidence of a possible small-scale Iraqi biological weapons effort and said searchers had substantial evidence of an Iraqi push to boost the range of its ballistic missiles beyond prohibited ranges.

But his team had found only limited evidence of any chemical weapons effort, he said. And there was almost no sign that a significant nuclear weapons project was under way.

Taken together, the findings do not appear to so far validate most of the Bush administration's prewar assertions of widespread and advanced Iraqi weapons programs, critics said.

Defense Secretary Donald H. Rumsfeld said Thursday "it will be unfortunate" if it turns out that intelligence used to justify the war in Iraq turns out to have been seriously flawed.

White House spokesman Scott McClellan said, however: "This detailed interim report documents how Saddam Hussein's regime was in clear violation of U.N. Security Council Resolution 1441." The resolution, which led to war, threatened Iraq with "serious consequences" if it failed to show it had handed over or destroyed its weapons of mass destruction.

"While Dr. Kay notes it is too early to reach conclusions, we are pleased with the progress being made to uncover the full extent of the regime's WMD programs, and we look forward to the final report," the spokesman said.

Six to nine months more

Kay said he should know within six to nine months if more is to be found in Iraq. The administration is asking for $600 million to continue the search, according to congressional officials.

"We have not found at this point actual weapons," Kay said after briefing Congress behind closed doors. "It does not mean we've concluded there are no actual weapons."

"In addition to intent, we have found a large body of continuing activities and equipment that were not declared to the U.N. inspectors when they returned in November of last year," he said.

But the lack of substantive findings brought immediate negative reactions from both Republicans and Democrats in Congress -- and also seemed certain to raise new questions among allies overseas about the Bush administration's justification for going to war.

"I'm not pleased by what I heard today, but we should be willing to adopt a wait-and-see attitude -- and that's the only alternative we really have," said Sen. Pat Roberts, R-Kan., chairman of the Senate Intelligence Committee.

Sen. Jay Rockefeller, D-W.Va., said of the Bush administration's justification for going to war: "Did we misread it, or did they mislead us, or did they simply get it wrong? Whatever the answer is, it's not a good answer."

The administration's assertions about Iraq's weapons programs and ties to terrorism, and the intelligence conclusions behind those assertions, had driven the administration's case for war.

Critics have contended that either the CIA and other agencies that make up the U.S. intelligence community made serious errors in their analysis or the administration exaggerated what intelligence information it did have to persuade a skeptical world to support an invasion.

Separately, CIA Director George Tenet, in a letter to the leaders of the House Intelligence Committee obtained by The Associated Press, rejected congressional criticism that the prewar intelligence findings were flawed.

Tenet's statement came in response to a blistering letter from Reps. Porter Goss, R-Fla., and Jane Harman, D-Calif., the chairman and ranking Democrat on the House Intelligence Committee. That letter, dated Sept. 25, cited "significant deficiencies with respect to the collection activities concerning Iraq's WMD and ties to al-Qaida prior to the commencement of hostilities there."

The findings cited by Kay included:

-- On biological weapons, a single vial of a strain of botulinum, a poison that can be used as a weapon, located at the home of a known biological weapons scientist.

-- On chemical weapons, multiple sources told the weapons hunting group that Iraq did not have a large, ongoing, centrally controlled program after 1991. There had been reports that Iraq retained some of its old chemical weapons but Kay said none had been found.

-- On nuclear weapons, Kay said in his statement to Congress that despite evidence of Saddam's continued ambition to acquire nuclear weapons, "to date we have not uncovered evidence that Iraq undertook significant post-1998 steps to actually build nuclear weapons or produce fissile material."

-- But on missiles, Kay said the team had "discovered sufficient evidence to date to conclude that the Iraqi regime was committed to delivery system improvements."

Kay also said Iraq conducted covert research into biological weapons by having scientists use benign substances and organisms as substitutes for those used to make a weapon. Some of the covert research also involved the Iraqi intelligence service, he said.

Kay listed a number of suspicious, but ultimately uncertain, discoveries of equipment and research that could apply to a weapons program. Discoveries of such "dual-use" equipment is often controversial because the items also have a legitimate use, often in chemical or pharmaceutical programs.

Kay said some of this equipment and laboratories wasn't declared to U.N. inspectors.

The inspectors, however, had found no fault with Iraq for failing to declare lots of equipment that could be deemed dual-use. Under U.N. Security Council resolutions, it was up to the council and the inspectors to decide what should have been declared. In any case, all equipment, included in the declaration or otherwise, was subject to monitoring by U.N. inspectors.

Kay also uncovered development efforts on a cruise missile with a 620-mile range, well beyond that allowed by the United Nations. But the missile was never completed, and development was halted when U.N. inspectors re-entered Iraq.

He also cited evidence, including documents, that Iraq attempted to acquire some long-range missile parts from North Korea, but any such deal was apparently never consummated.