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A University of Colorado professor who once compared some of the World Trade Center victims to a Nazi war criminal said Tuesday he mourns for everyone killed on Sept. 11 and conceded that he could have explained himself better.

Ward Churchill (search) made the comparison in an essay written hours after the 2001 attacks and later revised for a book. He called some victims "little Eichmanns," a reference to Adolf Eichmann, who organized the Nazi campaign to exterminate European Jews.

"I wouldn't retract it. I would explain it better," Ward Churchill told The Associated Press.

The essay, "Some People Push Back (search)," attracted little notice until last month, after Churchill was invited to speak at Hamilton College, a private liberal arts school. Hamilton professor Theodore Eismeier has said he found the essay on the Internet during what he calls "a casual effort to learn more about Churchill."

Churchill said he was referring to "technocrats" who participate in what he calls repressive American policies around the world. He said those include Iraqi trade sanctions after the first Gulf War that have been blamed for the deaths of 500,000 children.

"If someone were to ask me, 'Do you feel sorrow for the victims of 9-11,' of course I do," he said. "Let's begin with the children. Yes, they were innocent. And I mourn them. But they were not more innocent than those half-million Iraqi children."

The university backed off a threat to postpone a Tuesday night speech, saying students who claimed there were death threats had changed their stories. Earlier this month, Hamilton canceled Churchill's speech, citing death threats against the professor and its administrators.

More than a thousand people packed a ballroom Tuesday to hear him speak, mostly supporters.

In the interview with AP, Churchill said he did not mean to say the World Trade Center (search) "technocrats" were Nazis but were, like Eichmann, bureaucrats who participated in an immoral system.

"He did not necessarily agree with the goals of the Nazis with regard to the Jews, but he performed his functions brilliantly," Churchill said. "This is Eichmann: He's integral. The Holocaust could not have happened without him."

Churchill, an American Indian Movement (search) activist, said he shares some guilt because he participates in the system he accuses of wrongdoing: "I could do more. I'm complicit. I'm not innocent."

Gov. Bill Owens (search) has called for Churchill to be fired, and the university's Board of Regents is investigating whether the tenured professor of ethnic studies can be fired. Someone painted swastikas on the back of his pickup truck.

"I do not work for the taxpayers of the state of Colorado. I do not work for (Gov.) Bill Owens. I work for you," Churchill told the crowded ballroom Tuesday, to thunderous applause. "The regents should do their job and let me do mine."

In an e-mail to The Associated Press, Eismeier said he was alarmed by the "outlandish and odious rhetoric" and urged Hamilton administrators to withdraw Churchill's invitation. When they did not, he alerted the upstate New York school's student newspaper, which published a story about Churchill's writings Jan. 21.

Within days, the essay was national news. New York Gov. George Pataki called Churchill a "bigoted terrorist supporter" and the relative of one Sept. 11 victim called him a "nut case."

Scholars worry the backlash will leave other professors fearful of challenging conventional opinion.

"We recognize that academic freedom comes with limits, but we also know that any interference with academic freedom without strong cause sends a very chilling message to the entire academic community," said Barbara Bintliff, chairwoman of the Boulder Faculty Assembly.

David Horowitz, a champion of conservative causes who has long accused American universities of overstocking their faculties with leftists, said firing Churchill would violate his First Amendment rights and set a bad precedent.

He called instead for an inquiry into the university's hiring and promotion procedures "to see how Ward Churchill could get to the pinnacle of the faculty, to be the chair of an entire department."

"This isn't like a guy who was suddenly exposed," Horowitz said. "This is a guy who's been out in the open for 30 years and was promoted."