WASHINGTON - A third of the American public believes U.S. forces have found weapons of mass destruction in Iraq, according to a recent poll. Twenty-two percent said Iraq actually used chemical or biological weapons.

But such weapons have not been found in Iraq and were not used.

Before the war, half of those polled in a survey said Iraqis were among the 19 hijackers on Sept. 11, 2001. But most of the Sept. 11 terrorists were Saudis; none was an Iraqi.

The results startled even the pollsters who conducted and analyzed the surveys. How could so many people be so wrong about information that has dominated news coverage for almost two years?

"It's a striking finding," said Steve Kull, director of the Program on International Policy Attitudes at the University of Maryland, which asked the weapons questions during a May 14-18 poll of 1,256 respondents.

He added: "Given the intensive news coverage and high levels of public attention, this level of misinformation suggests some Americans may be avoiding having an experience of cognitive dissonance."

That is, of having their beliefs conflict with the facts. Kull noted that the mistaken belief that weapons had been found "is substantially greater among those who favored the war."

Pollsters and political analysts offer several reasons for the gaps between facts and beliefs: the public's short attention span on foreign news, fragmentary or conflicting media reports that lacked depth or skepticism, and Bush administration efforts to sell a war by oversimplifying the threat.

"Most people get little whiffs and fragments of news, not in any organized way," said Thomas Mann, a scholar at the Brookings Institution, a centrist-liberal think tank. "And there have been a lot of conflicting reports on the weapons."

Before the war, the U.S. media often reported as a fact the assertions by the Bush administration that Iraq possessed large stockpiles of illegal weapons.

During and after the war, reports of possible weapons discoveries were often trumpeted on front pages, while follow-up stories debunking the reports received less attention.

"There were so many reports and claims before the war, it was easy to be confused," said Larry Hugick, chairman of Princeton Survey Research Associates. "But people expected the worst from Saddam Hussein and made connections based on the administration's policy."

Bush has described the preemptive attack on Iraq as "one victory in the war on terror that began Sept. 11." Bush officials also say Iraq sheltered and helped al-Qaeda operatives.

"The public is susceptible to manipulation, and if they hear officials saying there is a strong connection between Iraq and al-Qaeda terrorists, then they think there must be a connection," Mann said.

"Tapping into the feelings and fears after Sept. 11 is a way to sell a policy," he added.

Polls show strong support for Bush and the war, although 40 percent in the May survey found U.S. officials were "misleading" in some of their justifications for war. A majority, 55 percent, said they were not misleading.

Several analysts said the murky claims and intelligence data about lethal weapons and terrorist ties allowed most people to see such news through the filter of their own political beliefs.

And GOP pollsters said any controversy over weapons won't change public attitudes, because ridding Iraq of an oppressive regime was reason enough for war for many Americans.

"People supported the war for national-security reasons, and that shifted to humanitarian reasons when they saw evidence of Saddam's atrocities," Republican strategist Frank Luntz said. "There's an assumption these weapons will be found because this guy was doing so many bad things."

Several analysts said they were troubled by the lack of knowledge about the Sept. 11 hijackers, shown in the January survey conducted for Knight Ridder newspapers. Only 17 percent correctly said that none of the hijackers was Iraqi.

"That really bothers me, because it shows a lack of understanding about other countries - that maybe many Americans don't know one Arab from another," said Sam Popkin, a polling expert at the University of California-San Diego who has advised Democratic candidates. "Maybe because Saudis are seen as rich and friendly, people have a hard time dealing with them as hijackers."

Hugick said his analysis showed those who were misinformed were not necessarily those who had less education.

"I think a lot of people are just confused about the threats out there," he said.