Iranian President Mahmoud Ahmadinejad was expected to visit Columbia University in New York City on Monday and deliver a speech there, but his presence in the most populous city in the United States sparked massive protests.

Protesters gathered outside the university early Monday before Ahmadinejad was due to arrive and deliver his speech on Morningside campus. Ahmadinejad’s ideology and harsh words have been heavily criticized by simple people, activists and politicians.

It is clear that most people do not welcome his presence in New York, but the acting dean of Columbia's School of International and Public Affairs, John Coatsworth, said Ahmadinejad is “an important person” because he is the “leader of an important country and one we are going to have to deal with in the future.”

Aside from defending the decision to invite Iran’s president at the world leaders forum, Coatsworth triggered public discontent when he said even Adolf Hitler would have been invited to speak before he “started the war and the Holocaust had begun,” as the Daily News reported.

One of the candidates for the Democratic nomination in the 2008 presidential election, Senator Hillary Rodham Clinton of New York criticized the university’s decision to invite Ahmadinejad saying she “would not have invited him.”

Clinton said Ahmadinejad is nothing but “a Holocaust denier and supporter of terrorism,” outlining he shouldn’t have been invited to deliver a speech in front of students.

An advocacy group, Freedom's Watch, published an ad in the New York Times on Monday in which it blasted the Iranian leader saying he is a “terrorist.”

Ahmadinejad “threatens our nation and the freedoms we value. He has supported attacks on our soldiers and our allies,” the group said

Ahmadinejad has been criticized in numerous rows in the United States for defying the sanctions imposed by the international community over Iran’s controversial nuclear program.

He refused to close the program which could be used to construct weapons of mass destruction and not for civilian purposes as Tehran sustains.

The Tehran government has been accused of undermining security in the Middle East by arming extremists in Iraq, Lebanon and the Palestinian territories, but the Iranian leader denied the accusations and lashed out at the Bush administration for trying to create instability.

In past statements he called for Israel’s destruction and denied that the Holocaust ever existed, sparking the anger of Jewish communities across the world.

He wanted to visit the site of the September 11, 2001 terrorist attacks to “pay his respects” during his stay in New York, but the American authorities rejected his request citing safety reasons.