Columbia ? Al Gore withdrew from an environmental conference in Miami on Friday to avoid appearing with the Colombian president, who is facing the most serious accusations yet that he aided far-right death squads.

Gore’s office said the former vice president did not want to appear at an event with President Alvaro Uribe until “this very serious chapter in history is brought to a close.”

Uribe said late Thursday that Gore’s decision was a sign of the damage caused by a growing scandal linking his political allies to Colombia’s illegal right-wing militias.

An opposition lawmaker in Colombia has alleged that Uribe let paramilitaries use his own property for meetings and killings while governor in a northern state in the mid-1990s.

Considered terrorist groups by the U.S. government, the paramilitaries are responsible for some of the worst massacres in Colombia’s long-running civil conflict. Many of the group’s commanders are wanted in the U.S. on charges of exporting hundreds of tons of cocaine.