BUENOS AIRES:  The Catholic Church stepped up its offensive against a gay marriage proposal, using Sunday Mass to urge its faithful to protest before Congress on the eve of a decisive Senate vote.

Argentina, where 91 percent of the population says it is Catholic, could become the first Latin American country to pass a law legalizing marriage between same-sex couples if the Senate adopts the bill before it on Wednesday.

The measure, which would grant the same rights to homosexual couples as heterosexual ones, cleared a first hurdle on May 5 in the lower chamber, but the Senate is gearing for a tougher battle.

During Sunday Mass, church officials read a message from Buenos Aires Archbishop Jorge Bergoglio in which he urged the faithful to protest Tuesday in front of Congress.

The bishops of La Pampa, a central province, published a document in which they defended a family model "with a mom and a dad, naturally endowed with the remarkable wealth of fertility."

Politicians are very divided on the subject and a Senate panel adopted an alternative project last week for civil unions that would bar gay couples from adopting, but the measure was not taken by the full chamber.

Argentines Alex Freyre and Jose Maria Di Bello were the first homosexuals to get married in Latin America, during a ceremony on December 28. Six other lesbian and gay couples did the same.

But a legal battle soon followed.

Judges tried to annul the gay marriages but the married couples have appealed the rulings every time, vowing to go all the way to the Supreme Court, if necessary.

BDST: 0946 HRS, 12 July 2010