NEW YORK, Sept. 24 -- Iranian President Mahmoud Ahmadinejad was greeted with student protests and withering public criticism during a visit to Columbia University Monday in which he defended his government's human rights record, denounced Israel and rejected U.S. efforts to restrict Iran's nuclear program.

Speaking to students and faculty at Columbia a day ahead of his scheduled address to the United Nations General Assembly, the hard-line Iranian president also asserted that his people, including women, "enjoy the highest levels of freedom," and he claimed that homosexuality does not exist in his country.

Before his speech, he came under unusually harsh criticism from Columbia University President Lee Bollinger, who condemned what he said was the Ahmadinejad government's expanding crackdown on dissent, its persecution of the B'hai religious minority and homosexuals, its support for the destruction of Israel and its pursuit of a "proxy war" against U.S. forces in Iraq.

"Mr. President, you exhibit all the signs of a petty and cruel dictator," Bollinger told Ahmadinejad from a podium across the stage. He said that the Iranian's denial of the Holocaust might fool "the illiterate and ignorant," but that "when you come to a place like this, it makes you quite simply ridiculous." Ahmadinejad's denial of the Holocaust suggested he was either "brazenly provocative or astonishingly uneducated," Bollinger said.

The university president's caustic comments were met with cheers and sustained applause from the roughly 700 people in the audience, most of them students.

Ahmadinejad called the introductory speech insulting and said Bollinger was misinformed. But he went on to repeat his assertions that the Holocaust should be researched "from different perspectives," and he denounced the punishment in Europe of "a number of academics" who were "questioning certain aspects of it." He also said Palestinians should not be "paying the price for an event they had nothing to do with."

In preparation for his arrival at Columbia, student groups including Jewish organizations and fraternities plastered the campus with posters. Many of them attacked Iran's human rights record and blasted statements in which Ahmadinejad dismissed the Holocaust and threatened Israel.

In a question-and-answer session following an opening statement, Ahmadinejad was asked whether he or his government sought the destruction of Israel as a Jewish state. He did not answer directly, instead calling for a "free referendum" in which Palestinians would "choose what they want for their future."

Pressed about the Holocaust, he said at one point, "I'm not saying that it didn't happen at all." Rather, he said, he is asking "what does it have to do with the Palestinian people?"

Ahmadinejad was also asked about the reported execution of homosexuals in Iran. In a rambling reply translated simultaneously from Farsi to English, he talked about the freedom of Iranian women and defended capital punishment for drug traffickers.

Eventually, he drew laughter and jeers when he said: "In Iran we don't have homosexuals like in your country. We don't have that in our country. In Iran we do not have this phenomenon. I don't know who told you that we have it."

Before his appearance at Columbia, Ahmadinejad spoke by video conference to the National Press Club in Washington, denying reports of human rights violations in Iran, defending his government's nuclear program and condemning what he said were U.S. efforts to "manage the world."

In response to questions, the Iranian leader asserted that "freedom is flowing at its highest level" in his country. "Our people are the freest people in the world, the most aware people in the world, the most enlightened." He added when asked about Iranian women, "The freest women in the world are women in Iran."

Ahmadinejad also denied that sophisticated Iranian weapons are being smuggled into neighboring Iraq and professed support for stability there. "We want nothing but goodness and progress for the Iraqi nation," he said.

Asked whether Iran were willing to go to war to protect its nuclear program, Ahmadinejad insisted that its efforts are "legal and for peaceful purposes." He said, "We think that talk of war is basically a propaganda tool."

The hard-line Iranian president arrived Sunday after stirring controversy with a request to visit and lay a wreath at Ground Zero, site of the Sept. 11, 2001, terrorist strike that destroyed the World Trade Center. City officials denied the request, a decision generally applauded by U.S. political leaders who said an appearance there by the leader of a reputed state sponsor of terrorism would have violated sacred ground.

Ahmadinejad told the National Press Club he had wanted to visit Ground Zero because "I was interested in expressing my sympathy to the victims of that tragedy" and because he wanted to comment on the need to "understand the root causes of events like 9/11." He did not specify what he meant by "root causes," but he added later: "We oppose the way the U.S. government tries to manage the world. We believe it is wrong. We believe it leads to war, discrimination and bloodshed."

At Columbia University, the Iranian leader said he had wanted to "show my respect" to the victims of the Sept. 11 attacks, and he expressed regret that "some groups" had vociferously objected, viewing such a visit as an insult.

"Why would you think that?" Ahmadinejad asked. But he also made another reference to "the root causes" of Sept. 11, which he said had "led to other events" around the world. "Afghanistan was occupied, and then Iraq was occupied," he said. "For six years in our region there has been insecurity, terror and fear."

He said he wanted to ask, "Who truly was involved" in Sept. 11. "Who was really involved and put it all together?"

On the university campus, the Iranian's visit brought out protesters from a variety of groups.

"Stop Ahmadinejad's Evil," said a black T-shirt being distributed by a Jewish student group for protesters to wear at the Iranian president's campus speech.

Sarah Brafman, one of the students handing out the T-shirts, said that while she opposes Ahmadinejad, his appearance provided an opportunity to promote freedom of speech.

"Students do want to hear what he has to say," the Columbia sophomore said before the speech. "He's a heavy player in world politics. But this is a platform for us as much as it is for him, to expose what he's really made of."

Other protesters opposed the decision of Columbia's School of International and Public Affairs to invite Ahmadinejad in the first place, saying the school should not provide a forum for a "terrorist."

Maryam Jazini, a Fordham Law School student of Iranian descent, said, "I really don't like him, but I don't think he represents what Iranians are." Wearing a white head scarf, Jazini helped other members of Columbia's unofficial Persian Philosophy Club put up large signs saying that Iranians were among the first to condemn the Sept. 11 attacks.

Another demonstrator, Jack Orleans, had sharp words for both Ahmadinejad and President Bush. "We refuse to choose between Bush and Ahmadinejad," said large orange signs he was posting on campus.

"We can't allow our choices to be limited to Islamic fundamentalism on the one hand and the Bush administration crusading around the world for empire on the other," he said. "Humanity needs another way."

Other posters mocked the visiting Iranian president. "Bringing Sexy Back," one said under a photo of Ahmadinejad. "Nerd Alert," said another.

"The Evil Has Landed," read the front-page headline of the New York Daily News.

Commenting on the Iranian's visit, Secretary of State Condoleezza Rice told the CNBC cable TV channel Monday it would have been a "travesty" if he had been allowed to visit Ground Zero.

"This is somebody who is the president of a country that is probably the greatest sponsor -- state sponsor -- of terrorism, someone who is a Holocaust denier, someone who has talked about wiping other countries off the map," Rice said. "I think it would have been a travesty." She referred to statements in which Ahmadinejad dismissed the Holocaust as a "myth" and said that Israel "must be wiped off the map."

On Tuesday Ahmadinejad is scheduled to address the U.N. General Assembly. Under terms of his visit to New York City, he is not allowed to travel outside a 25-mile radius.

Ahead of his appearance, Ahmadinejad said in an interview broadcast Sunday night that Tehran has no need for a nuclear weapon and challenged claims that his country is arming Iraqi militants targeting U.S. troops.

Ahmadinejad also said that tensions between the United States and Iran, which have steadily heightened over Tehran's nuclear ambitions and support for extremists, are not headed toward a military confrontation.

"It's wrong to think Iran and the U.S. are walking towards war," he said on CBS's "60 Minutes" program. "This is psychological warfare. If you have differences of opinion, you can use logic to resolve your differences."

The hard-line leader said Iran does not need a nuclear bomb because such weapons have not guaranteed security even for superpowers. "In political relations right now, the nuclear bomb is of no use. If it was useful, it would have prevented the downfall of the Soviet Union. If it was useful, it would have resolved the problem the Americans have in Iraq," he said.

Although Iran had a secret uranium enrichment program for almost two decades, Ahmadinejad said that Iran now has "nothing to hide."

He scoffed at U.S. allegations that his country has provided deadly roadside bombs known as explosively formed projectiles to Iraqi extremists. "It's laughable for someone to turn a blind eye to the truth and accuse others," he said in the interview, taped in Tehran. "It doesn't help. And the reason that I'm smiling again is because the picture is so clear. But American officials refuse to see it."

Ahmadinejad said that instability in Iraq is "detrimental" to Tehran's regional interests.

Branigin reported from Washington.