SAN JOSE: Costa Rica's president Oscar Arias declared victory Sunday in his drive to join a free trade deal with the United States, announcing on television that voters had backed it in a referendum.

"The people of Costa Rica have said yes to the free trade agreement, and that for me is a sacred wish," Arias said in a televised address to the nation after Costa Ricans voted in their tens of thousands on the measure.

Earlier partial results showed that with 73 per cent of votes counted, just over 50 per cent of voters said yes to the agreement against 47.5 per cent who voted no, the Supreme Electoral Tribunal said. Turnout was around 60 per cent.

The Central American Free Trade Agreement is to open local markets to US products but also boost Costa Rican exports to the United States.

It has been accepted by several other countries in the region, but faced left-wing opposition in Costa Rica, where Arias was forced to call a referendum on it after more than three years of domestic debate. - AFP/ac