Leaders at Wednesday's summit in Nicaragua blamed US trade policies for the region's food crisis.
President Hugo Chavez says he is willing to talk with Colombia's rebel FARC for the release of three US defense contractors.
President Mahmoud Ahmadinejad stops in India Tuesday after visiting Pakistan and Sri Lanka on a trip aimed at inking energy deals and curbing the West's influence.
The four countries, joined in a trading bloc called ALBA, said they would step up agricultural production efforts.
A win by Fernando Lugo, a former liberal priest, would follow a leftist trend in South America.