The South American group, known as the Andean Community, has been divided over a possible trade deal with the European Union, and over member nations' separate trade pacts with other countries, including the U.S.
The group also has its own agreement on intellectual property laws, and must approve any changes that members might make to their own related laws.
Ecuador and Bolivia have criticized Peru's freer trade stance, and Bolivian opposition has stalled trade talks between the Andean Community and the EU. The two nations have opposed past attempts to change the group's trade policies, arguing that Peru's trade deal with the U.S. impedes regional integration.
But Ecuador reversed course Thursday, joining Colombia and Peru in backing the change during a second round of voting, Peru's Trade Minister Mercedes Araoz said.
Peru had lobbied its neighbors to back the change since signing the U.S. trade deal two years ago.
The U.S. Congress approved the trade deal last December. As required by the treaty, Peru is now adapting its laws to U.S. regulations - making changes at home that include boosting workers' rights to strike - in hope of implementing the agreement in early 2009.