ISTANBUL (AP) — About a week ago, Iranian President Mahmoud Ahmadinejad declared to the United Nations that most people in the world believe the United States was behind the terrorist attacks of Sept. 11, 2001.

To many people in the West, the statement was ludicrous, almost laughable if it weren’t so incendiary. And surveys show that a majority of the world does not in fact believe that the U.S. orchestrated the attacks.

However, the belief persists strongly among a minority, even with U.S. allies like Turkey or in the U.S. itself. And it cannot be dismissed because it reflects a gulf in politics and perception, especially between the West and many Muslims.

"That theory might be true," said Ugur Tezer, a 48-year-old businessman who sells floor tiles in the Turkish capital, Ankara. "When I first heard about the attack I thought, ‘Osama,’ but then I thought the U.S. might have done it to suppress the rise of Muslims."

Compassion for the United States swept the globe right after the attacks, but conspiracy theories were circulating even then. It wasn’t al-Qaida, they said, but the United States or Israel that downed the towers. Weeks after the strikes, at the United Nations, President George W. Bush urged the world not to tolerate "outrageous conspiracy theories" that deflected blame from the culprits.

However, the subsequent wars in Iraq and Afghanistan provided fodder for the damning claim that the U.S. killed its own citizens, supposedly to justify military action in the Middle East and to protect Israel. A 2006 survey by the Pew Global Attitudes Project found that significant majorities in Egypt, Indonesia, Jordan and Turkey — all among the most moderate nations in the Islamic world — said they did not believe Arabs carried out the attacks.

Two years later, a poll of 17 nations by WorldPublicOpinion.org, an international research project, found majorities in nine of them believed al-Qaida was behind the attacks. However, the U.S. government was blamed by 36 percent of Turks and 27 percent of Palestinians.

Such beliefs have currency even in the United States. In 2006, a Scripps Howard poll of 1,010 Americans found 36 percent thought it somewhat or very likely that U.S. officials either participated in the attacks or took no action to stop them.

Those who say the attacks might have been an "inside job" usually share antipathy toward the U.S. government, and often a maverick sensibility. Besides Ahmadinejad, high-profile doubters include Cuba’s Fidel Castro and Venezuelan President Hugo Chavez. Former Minnesota governor and pro wrestler Jesse Ventura has questioned the official account. Conspiracy theorists have heckled former President Bill Clinton and other prominent Americans during speeches.

Controversy over U.S. actions and policies, including the widely discredited assertions that Saddam Hussein had weapons of mass destruction, reinforced the perceptions of conspiracy theorists. Iranians dug deeper into history, recalling the U.S.-backed coup in their country in 1953.

"Initially, I was doubtful about the conspiracy theories. But after seeing the events in later years, I don’t have any doubt that it was their own operation to find a pretext to hit Muslim countries," said Shaikh Mushtaq Ahmed, a 58-year-old operations manager in a bank in Pakistan. "It’s not a strange thing that they staged something like this in their own country to achieve a big objective."

In March, an editorial in The Washington Post harshly criticized Yukihisa Fujita, a lawmaker with the ruling Democratic Party of Japan, for saying in an interview that some of the Sept. 11 hijackers were alive and that shadowy forces with advance information about the plot played the stock market for profit. Fujita said the article contained factual errors.

The record shows that al-Qaida agents on a suicide mission hijacked four American passenger planes and crashed them into the World Trade Center towers, the Pentagon, and a field in Pennsylvania, killing nearly 3,000 people. The evidence is immense: witness accounts, audio recordings, video and photographic documentation, exhaustive investigations and claims of responsibility by al-Qaida.

Yet every fact and official assertion only feeds into alternative views that become amplified on the Internet, some tinged with anti-Semitism because of the close U.S.-Israeli alliance. They theorize that a knowing U.S. government stood by as the plot unfolded, or that controlled demolitions destroyed the Twin Towers, and the Pentagon was hit by a missile.

"All this, of course, would require hundreds if not thousands of people to be in on the plot. It speaks volumes for the determination to believe something," said David Aaronovitch, the British author of "Voodoo Histories: the role of Conspiracy Theory in Modern History."

"This kind of theory really does have a big impact in the Middle East," he said. "It gets in the way of thinking seriously about the problems in the area and what should be done."

A U.S. State Department website devotes space to debunking conspiracy theories about Sept. 11, in the apparent belief that the allegations must be addressed forcefully rather than dismissed out of hand as the ruminations of a fringe group.

"Conspiracy theories exist in the realm of myth, where imaginations run wild, fears trump facts, and evidence is ignored. As a superpower, the United States is often cast as a villain in these dramas," the site says.

Tod Fletcher of Petaluma, California, has worked as an assistant to David Ray Griffin, a retired theology professor, on books that question the Sept. 11 record. He was cautious about the Iranian president’s comments about conspiracy theories, suggesting Ahmadinejad may have been politically motivated by his enmity with the U.S. government.

"It seems like it’s the sort of thing that could lead to further vilification of people who criticize the official account here in the United States," Fletcher said.

Torchia reported from Istanbul. Associated Press Writers Gulden Alp in Ankara, Turkey, and Zarar Khan in Islamabad contributed to this report.