Venezuelan President Nicolas Maduro is criticizing a weekend visit by former leaders of Mexico, Chile and Colombia, accusing them of inadvertently lending support to extremist groups trying to oust him from power.

Felipe Calderon of Mexico, Sebastian Pinera of Chile and Andres Pastrana of Colombia are expected to participate in a pro-democracy symposium organized by Maduro's opponents. They're also expected to try to visit jailed opposition leader Leopoldo Lopez.

Maduro is struggling to rebuild Venezuela's oil-dependent economy amid spiraling inflation and widespread shortages, and he said at a rally Thursday that the three conservative former presidents would have "blood on their hands" for backing for his opponents.

He accused Calderon of ties with drug traffickers and called Pinera a supporter of former Chilean dictator Augusto Pinochet.