El Salvador is entering into a free-trade agreement with the United States Wednesday, after demonstrations against it in the country's capital.
Students and labor union members marched in the streets of San Salvador Tuesday and clashed with police who were trying to contain the crowds. At least five people were injured.
Critics of the trade pact say it will hurt small businesses and organized labor. It also requires participating countries to crack down on pirated merchandise, which has angered street vendors.
Guatemala, Costa Rica, Honduras, Nicaragua, and the Dominican Republic are also expected to enter into the pact, known as the Central American Free Trade Agreement, after meeting entrance requirements.
Guatemalans staged anti-CAFTA rallies in Guatemala City last week.
Some information for this report was provided by AP.