SAN JOSE ? A constitutional court in Costa Rica on Tuesday derailed a Catholic Church-supported national referendum on whether the country should grant same-sex couples the right to civil unions.

The vote was scheduled for December 5 and in this highly Catholic country was expected to reject the possibility of granting same-sex couples the same rights as their married counterparts.

But the Supreme Court ruled that the rights of minorities could not be determined by a popular vote and that the issue should be decided by the country's lawmakers.

"Minority rights that are derived from claims against the majority cannot be subject to a referendum process where majorities are needed," the court said in a statement.

The vote sought to ask Costa Ricans whether the Central American nation should grant same-sex couples some of the rights of married couples, such as in inheritance, health insurance benefits and the right to family visits in case of hospitalization.

Draft legislation legalizing same-sex civil unions was presented before the country's lawmakers in 2008, but has been frozen since. The court's decision, which cannot be appealed, is expected to relaunch debate on the subject.

Conservative groups linked to religious organizations gathered some 150,000 signatures in favor of the referendum.

But the court said Tuesday that "people who have relationships with individuals of the same sex form a group that is subject to disadvantages and discrimination, and require the support of public authorities to obtain their rights."

A number of Latin American countries, including Uruguay and Colombia, already permit same-sex civil unions.

On Thursday, Mexico's Supreme Court ruled Mexico City's gay marriage law constitutional, defeating a challenge to the measure by President Felipe Calderon's conservative administration.

Argentina last month became the first country in Latin America to legalize same-sex marriage when President Cristina Kirchner signed a law to that effect on July 21.

Nine days later, two men became the first couple wed under the law in a civil ceremony in Buenos Aires.