SAN JOSE, Costa Rica – Costa Ricans prepared yesterday to join a controversial free trade agreement with Central American neighbors, the Dominican Republic and the U.S. after a thin majority apparently backed the pact in a national referendum.

But even Sunday’s vote on the Central American Free Trade Agreement did not end a yearlong battle over the agreement.

Opponents said they will wait for a mandatory recount, set to begin today, before recognizing the referendum’s results. The ballot-by-ballot recount is required by Costa Rican law, and can last no longer than two weeks.

With 97 percent of precincts reporting yesterday, 51.5 percent of Costa Ricans voted in favor of the trade deal, which is known as CAFTA.

Costa Rica was the lone holdout among the six Latin American nations that now constitute the trade bloc. The pact has already taken effect in the Dominican Republic, Guatemala, Honduras, Nicaragua and El Salvador.

The White House kept a close eye on Sunday’s election results, having fought a bruising political battle to get the deal ratified by the U.S. Congress in 2005, when it passed the House of Representatives by just two votes.