By Leta Hong Fincher, VOA, Washington

As Iranian President Mahmoud Ahmadinejad continues his controversial visit to the United States, Iran has emerged as a major issue in the 2008 U.S. presidential campaign. Leading candidates for the presidency are presenting different approaches to what they see as a growing threat from Iran's suspected nuclear weapons program. VOA's Leta Hong Fincher has more on what some of the presidential contenders are saying.

Mahmoud Ahmadinejad speaks at Columbia University in New York, 24 Sept 2007

Mr. Ahmadinejad's appearance at Columbia University in New York on Monday, September 24th, sparked outrage among some of the Republican presidential contenders. But former Massachusetts Governor Mitt Romney was the only candidate to oppose the United Nations' decision to allow Mr. Ahmadinejad to speak to the General Assembly on Tuesday.

Mr. Romney, a Republican presidential candidate commented, "It's simply unacceptable to bring a man to the world stage who has called for the elimination of another nation, has called for, in various terms, genocide, and is developing, contrary to the demands of the United Nations, nuclear weapons that would allow him to carry out genocide."

Romney has called for Mr. Ahmadinejad to be indicted for genocide, and he says there should be tighter sanctions against Iran.

Another Republican presidential candidate, former New York Mayor Rudy Giuliani, has repeatedly said the United States must make it clear that it will not allow Iran to become a nuclear power. Giuliani said in a presidential debate in June that he would not rule out using "tactical" nuclear weapons against Iran.  "Iran is a threat, a nuclear threat and not just because they can deliver a nuclear warhead with missiles. They are a nuclear threat because they are the biggest state sponsor of terrorism and they can hand nuclear materials to terrorists."

Other leading Republican presidential contenders agree that the United States should not rule out military action against Iran to keep it from developing nuclear weapons.

Candidates from the Democratic Party vary more on how they say they would treat Iran, but many are calling for intensified diplomatic efforts.

Senator Barack Obama says he finds many of Mr. Ahmadinejad's statements "odious." But Obama says he would be willing, as president, to meet with the Iranian leader to protect U.S. interests. "As John F. Kennedy said, 'We should never negotiate out of fear, but should never fear to negotiate.' And by us listening to the views of even those who we violently disagree with, that sends a signal to the world that we are going to turn the page on the failed diplomacy that the Bush administration has practiced for so long."

Obama has clashed with his Democratic rival, Senator Hillary Clinton, over their foreign policy judgment. At a debate in July, Obama said he would be willing to meet with foreign leaders -- including those of Iran and North Korea -- without preconditions.

Clinton criticized Obama's remarks as "irresponsible and naïve."  She said she would not promise to meet any leaders without preconditions because she did not want to be used for "propaganda purposes." "I will use a lot of high-level presidential envoys to test the waters, to feel the way," she said. "But certainly we're not going to just have our president meet with Fidel Castro and Hugo Chavez and, you know, the president of North Korea, Iran and Syria until we know better what the way forward would be."

Both Clinton and Obama say they do not rule out military force against Iran to keep it from developing nuclear weapons.