Iranian President Mahmoud Ahmadinejad will be visiting Latin America this week for the fifth time since 2007 – as often as U.S. presidents over the same period, and visiting more countries than they did. He must have powerful reasons to spend so much time in the region.

Ahmadinejad's five-day trip to Venezuela, Nicaragua, Cuba and Ecuador – which U.S. House Foreign Relations Committee chairwoman Ileana Ros-Lehtinen, R- Fla., has labeled a "tour of tyrants" – comes at a time of growing international tensions over Iran's failure to comply with United Nations nuclear non-proliferation agreements.

The United States and the 27-country European Community have announced new economic sanctions on Iran, including a possible European oil embargo, following a November United Nations report that Iran is likely to be developing a nuclear bomb. Iran is threatening to close the Strait of Hormuz, where 35 percent of the world's oil goes through, if U.S. and European sanctions limit its oil exports.

There are two major theories within the U.S. diplomatic community on Ahmadinejad's trip.

U.S. foreign policy hard-liners, including most Republican presidential candidates, say Iran's growing presence in Latin America is a demonstration of power by a terrorist regime.

"The Iranians have a vision of themselves of being a global power, and they feel that they have the momentum," says Roger Noriega, a Republican foreign policy hawk who headed the U.S. State Department's Latin American affairs office during the George W. Bush presidency.

"They feel that they blocked the U.S. presence in Iraq, they are angling to undermine the U.S. agreement with Afghanistan, and they want to challenge us in our neighborhood," he adds.

According to Noriega, Iran is getting help from Venezuela, and perhaps from Ecuador, to mine uranium for its nuclear program. In addition, Iran is building a network of local operatives in Latin America to strike back at U.S. and Israeli targets in the region should there be a military attack against Iran's nuclear facilities, Noriega says.

The United States says Iran is the world's leading sponsor of terrorism, providing weapons to several terrorist groups and actively promoting suicide bombings in the Middle East. Argentina has also accused Iran of carrying out bloody bombings against the Israeli Embassy and a Jewish community center in 1992 and 1994.

U.S. foreign policy moderates, on the other hand, side with the State Department's view that Ahmadinejad's visit to Latin America may be a sign of weakness.

The Iranian leader is increasingly isolated at home and abroad, and is desperately seeking to project an image of strength by showing his countrymen that he is being welcomed abroad, U.S. moderates say.

At home, Ahmadinejad has lost the support of the nation's fundamentalist supreme leader, Ayatollah Ali Khamenei, and at the same time faces a growing challenge from reformist leaders such as presidential hopeful Mir Hossein Mousavi.

Iran's economy is deteriorating badly, and new international sanctions could make things worse. Rising food prices could drive up public discontent, which has already risen significantly since the regime's brutal repression of protests over Ahmadinejad's dubious 2009 electoral victory.

Meantime, Syria's regime – Iran's closest Middle Eastern ally – is increasingly threatened by an internal revolt.

Asked about Ahmadinejad's trip, a well-placed State Department official told me that it's a frantic effort to break his growing domestic and international isolation. As for allegations that Iran is getting nuclear cooperation from Venezuela, and may be creating local terrorist networks in the region, the official said that "Iran's threat to the U.S. national security interests in Latin America is latent, rather than active."

My opinion: I tend to side with the moderates, in that Iran's fascist ruler is trying to show his people at home that he is not a world pariah, and that he is still received as a world figure abroad.

Still, the Latin American presidents who are welcoming him are not only embracing a tyranny – which according to Amnesty International severely restricts fundamental freedoms and executed up to 552 people last year, more than any other country except China – but may also be setting up violent support groups in Latin America to use as an insurance policy against an attack against its nuclear facilities.

By welcoming Ahmadinejad, they are importing a foreign conflict, and that can only bring bad things to the region. The 1990's bombings in Argentina speak for themselves.

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Andres Oppenheimer is a Latin America correspondent for the Miami Herald.

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