Argentina's Senate is expected to take a decisive vote on a gay marriage bill Wednesday, two months after the law cleared the nation's lower house, the Chamber of Deputies.

The Senate General Law Committee, however, has recommended the Senate reject the marriage proposal and instead take up a bill that recognizes gay couples with civil unions but does not allow for adoption.

Tens of thousands of people Tuesday rallied against the bill in the nation's capital city of Buenos Aires. At the rally, sponsored by the Roman Catholic Church, to which 91% of the population claims allegiance, people held banners that read “We want a mommy and daddy,” “Praise the family,” and “We support the real family.”

A crowd of approximately 1,000 pro-gay marriage activists held a counter rally at a nearby monument.

In calling on Catholics to reject gay marriage, the church called the bill the devil's handiwork. Buenos Aires Archbishop Jorge Bergoglio said the movement was backed by “the Father of Lies” and “aims to confuse and deceive the children of God.”

Calling the church's tone reminiscent of “medieval times and the Inquisition,” President Cristina Fernandez de Kirchner, who supports the legislation, chided the church.

“It is disturbing to hear phrases like war of God or the devil's projects, which are things that take us back to medieval times and the Inquisition,” Kirchner told the Argentine press during an official visit to China.

As of Wednesday morning, analysts in the Argentine press were predicting the measure would be approved by a narrow majority, provided 3 objecting senators abstain.

Some critics have charged that the president is peddling the issue to boost her family's political dynasty. Former president Nestor Kirchner, now a congressman, is expected to try to regain the presidential palace next year.

Polling shows that nearly 70 percent of Argentinians support marriage equality for gay and lesbian couples.

If approved, Argentina would become the first Latin American country to legalize gay marriage. The institution is also legal in Mexico City, but the federal government is challenging the law in court.