Democrat Barack Obama says he probably wouldn't have invited Mahmoud Ahmadinejad to speak at Columbia University but would be willing as president to meet with the Iranian leader as a way to protect U.S. interests.

"The hateful lies that he may utter about Israel, the Holocaust -- the answer is for us to promote the truth and show the world the values and ideals that we hold dear," Obama said Monday. "One of the values we believe in is the value of academic freedom. He has a right to speak."

Obama earned a bachelor's degree in 1983 from Columbia, where the Iranian president spoke on Monday. The Illinois senator was asked about the appearance at a news conference where he was endorsed by New York City's Correction Officers' Benevolent Association.

Columbia has come under heavy criticism for providing a forum to Ahmadinejad, who has called the Holocaust "a myth" and has said Israel should be "wiped off the map."

Democratic candidate John Edwards said Monday of such statements: "I find all those things abhorrent." He added, "I think this is for Columbia to decide whether they want a man like this to speak at their university."

As for meeting with foreign leaders the U.S. does not have good relations with, Edwards said in Washington that he would "do what's in the best interest of the security of the United States of America. ... In the case of a leader like Ahmadinejad, Kim Jong Il, Hugo Chavez, any of these leaders, you have to be extraordinarily careful they would not use such a meeting for PR purposes and for propaganda purposes."

Separately, Republican Mitt Romney began running radio ads in South Carolina and Iowa urging the United Nations to withdraw its invitation to Ahmadinejad to speak to the General Assembly on Tuesday. He said, "What we should be doing is indicting Ahmadinejad under the Genocide Convention."

The ad says that Romney, as governor of Massachusetts, opposed former Iranian President Mohammad Khatami's 2006 visit to Harvard and refused to give Khatami a state police escort.

In Chicago for a fundraiser, Republican candidate John McCain told reporters it was astonishing that Columbia would invite Ahmadinejad, citing Iran's hostility toward Israel and potential weapons exported to Iraq.

The Arizona senator said Ahmadinejad should be allowed at the United Nations, but shouldn't have been given a forum to convey "the policies of hate and destruction which would characterize Iran's behavior towards the United States particularly as far as Iraq is concerned."

Like Obama, McCain has a personal link to Columbia. His daughter, Meghan, graduated from the college earlier this year.

In Maine, Republican Rudy Giuliani echoed McCain's criticism of Ahmadinejad and questioned Columbia's invitation.

"I think its highly inappropriate that Columbia University asked him to speak. ... His government of Iran is considered to be the single biggest state sponsor of terrorism in the world," Giuliani said.

Said Republican Fred Thompson: "Columbia University gave a public forum today to a tyrant to spread his lies and deceit."

Obama said there was no contradiction between his willingness to meet with Ahmadinejad as president and his statement that he probably would not have invited him to Columbia.

"As president of the United States, my job is to look out for the national security interests of this country. Iran, in particular because of the bad decision this administration has made by invading Iraq, is a major player in the Middle East," Obama said. "If it is in the United States' interest to make certain that we can stabilize the situation and avoid further military confrontation and curb state sponsored terrorism they've been involved with, that's something we should be willing to do."

He said the Columbia appearance was unnecessary because Ahmadinejad would have other opportunities during his visit to New York to make his views known.

Obama was criticized by rival Hillary Rodham Clinton and other Democrats after a debate in July in which he said he would be willing to meet with Ahmadinejad and leaders of other nations the U.S. is not on good terms with "without precondition" as president. Clinton called Obama's remark irresponsible and naive and suggested it was evidence he did not have sufficient experience to be president.

President Bush said Monday that if Columbia "thinks it's a good idea to have the leader from Iran come and talk to the students as an educational experience, I guess it's OK with me."

Bush, in an interview with Fox News Channel, said, "I'm not so sure I'd have offered the same invitation." However, he said, "I mean when you really think about it, he's the head of a state sponsor of terror, he's -- and yet an institution in our country gives him a chance to express his point of view, which really speaks to the freedoms of the country."