Ahmadinejad added Guatemala to his itinerary to take part in the inauguration of President-elect Otto Perez, a ceremony that will be attended by at least 11 other heads of Latin American and Caribbean states. Prince Felipe de Borbon, heir to the Spanish crown, is also to attend.
Ahmadinejad last visited Latin America in 2009 and later was host to former Brazilian President Luiz Inacio Lula da Silva, Venezuelan President Hugo Chavez and numerous other senior officials from Central and South America.
The Iranian visit is the second recent instance of Latin American governments' policies moving markedly away from Washington, after last year's support to Palestinian statehood and recognition of a future Palestinian state.
Ahmadinejad's last visit to the region raised the specter of sweeping U.S. government sanctions on countries dealing with Iran.
But such retaliation became difficult after Brazil joined the campaign to bring Iran to the conference table over its nuclear program. Iran initiated a wide range of trade finance and economic collaboration deals and is likely to pursue of the same during the coming visit.
Brazil and Turkey are engaged in talks to cool temperatures between Iran and the West over the nuclear controversy.
After the last visit, The Economist wrote: "The United States government stayed silent on the subject of President Ahmadinejad's visit to Brazil. But its annoyance at seeing the Iranian leader embraced so warmly in its backyard may be tempered by the thought that at least there is now a line of communication open, via Brasilia, to Tehran."
U.S. President Barack Obama visited Brazil last March and is actively seeking a regeneration of diplomatic and trade ties with all of Latin America, including countries that are seen to be closer to Tehran than to Washington, in particular Venezuela.
Iran is pursuing a similar aim. The official IRIB News Agency said, "The promotion of all-out cooperation with Latin American countries is among the top priorities of the Islamic Republic's foreign policy."
Ahmadinejad will begin his visit in Venezuela, where he will meet Chavez, then fly to Managua to attend the swearing-in ceremony for Nicaraguan President Ariel Ortega following his recent re-election.
Talks in Cuba and Ecuador will follow.
Plans for Ahmadinejad's visit coincide with continuing tensions over Iranian actions in the strategic Persian Gulf oil waterway, the Strait of Hormuz.
The Pentagon snubbed an Iranian warning not to return a U.S. aircraft carrier to the region, saying Washington will operate there as it has for decades.
The U.S. Navy's nuclear-powered aircraft carrier John C. Stennis will operate in the region to maintain security and stability, Pentagon spokesman George Little said after Iran's army commander in chief told Washington the carrier, which left the Persian Gulf through the Strait of Hormuz last week, shouldn't return.
Roughly one-fifth of all the crude oil traded worldwide passes through the narrow strait.
Iran's economy, battered by Western sanctions over its nuclear program -- which U.S. and European officials allege is to build nuclear weapons -- received another hit Saturday when Obama signed a bill that could penalize buyers of Iranian oil.
Iran, the world's No. 3 energy exporter, relies on oil exports to finance as much as half its national budget.
It also insists its nuclear goal is to generate electricity without dipping into its reserves of oil Iran would prefer to sell abroad and to provide fuel for medical reactors.