President Ahmadinejad of Iran, facing protests and tabloid headlines calling him “evil” and a “madman,” stirred debate today about free speech ahead of his appearance at Columbia University.

The president of Columbia University, Lee Bollinger, has promised to grill Mr. Ahmadinejad on subjects such as human rights, the Holocaust, and Iran’s disputed nuclear program. The Iranian leader previously has called the Holocaust “a myth” and called for Israel to be “wiped off the map.”

Mr. Bollinger said today it was a question of free speech and academic freedom.

“It’s extremely important to know who the leaders are of countries that are your adversaries. To watch them to see how they think, to see how they reason or do not reason. To see whether they’re fanatical, or to see whether they are sly,” he told ABC’s “Good Morning America.”

Mr. Ahmadinejad is to speak and answer questions at a Columbia forum today, followed by a scheduled address to the U.N. General Assembly tomorrow.

Tensions are high between Washington and Tehran over American accusations that Iran is secretly trying to develop nuclear weapons, as well as helping Shiite militias in Iraq that target American troops — claims Iran denies.

“Well, you have to appreciate we don’t need a nuclear bomb. We don’t need that. What need do we have for a bomb?” Mr. Ahmadinejad said in a “60 Minutes” interview that aired yesterday, taped earlier in Iran. “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.”

He also said that: “It’s wrong to think that Iran and the U.S. are walking toward war. Who says so? Why should we go to war? There is no war in the offing.”

Before leaving Iran, Mr. Ahmadinejad said the American people have been denied “correct information,” and his visit will give them a chance to hear a different voice, the official IRNA news agency reported.

Mr. Ahmadinejad has appealed to the American people before, distinguishing between the population and their government. Recently, he told a television show that Iran wants peace and friendship with America. Since coming to power in 2005, Mr. Ahmadinejad also has sent letters to the American people criticizing President Bush’s policies in the Middle East.

Washington has said it is addressing the Iran situation diplomatically, rather than militarily, but American officials also say that all options are open. The commander of the American military forces in the Middle East said he did not believe tensions will lead to war.

“This constant drum beat of conflict is what strikes me, which is not helpful and not useful,” Admiral William Fallon, head of U.S. Central Command, told Al-Jazeera television, which made a partial transcript available yesterday.

Mr. Ahmadinejad’s scheduled address to the U.N. General Assembly tomorrow will be his third time attending the New York meeting in three years.

His request to lay a wreath at ground zero was denied by city officials and condemned by politicians who said a visit to the site of the 2001 terror attacks would violate sacred ground.

Police cited construction and security concerns in denying Mr. Ahmadinejad’s request. Mr. Ahmadinejad told “60 Minutes” he would not press the issue but expressed disbelief that the visit would offend Americans.

After the September 11, 2001 attacks, hundreds of young Iranians held a series of candlelight vigils in Tehran.

“Usually you go to these sites to pay your respects. And also to perhaps air your views about the root causes of such incidents,” Mr. Ahmadinejad told the network.

Columbia canceled a planned visit by the Iranian president last year, also citing security and logistical reasons. This time, security on campus was tight hours ahead of his arrival, with barriers blanketing the grounds and police patrolling.

Protest signs emblazoned with some of Mr. Ahmadinejad’s most notorious quotes about Israel were posted on campus, many by the Columbia Barnard Hillel group.

A 25-year-old graduate student in environmental engineering, Sam Krevor, said he’s watched some interviews with the Iranian president before.

“I appreciate that the event is happening, but even when he gets hard questions he’s not particularly interested in answering them,” Mr. Krevor said. “I think it’s doubtful that the actual event will be that enlightening.”

Mr. Ahmadinejad’s visit to New York is also being debated back home. Some in Iran think his trip is a publicity stunt that hurts Iran’s image in the world.

A political analyst, Iraj Jamshidi, said Mr. Ahmadinejad looks at the General Assembly as a publicity forum simply to surprise world leaders with his harsh rhetoric.

“The world has not welcomed Ahmadinejad’s hardline approach. His previous address to the assembly didn’t resolve any of Iran’s foreign policy issues. And no one expects anything better this time,” he said.

But a conservative lawmaker, Alaeddin Boroujerdi, said it was a good chance for Iran to air its position.

“This trip gives the president a good chance to meet world leaders and inform them of Iran’s rightful position,” IRNA quoted Mr. Boroujerdi as saying.