By Rafael Romo, Jose Manuel Rodriguez and Catherine E. Shoichet, CNN

Buenos Aires (CNN) - Less than an hour after he sent Catholic Church leaders in Argentina a letter in 2010 criticizing the way they were handling the debate over same-sex marriage, Marcelo Marquez says his phone rang.

He was surprised to hear the voice on the other end of the line. It was Jorge Mario Bergoglio, then the archbishop of Buenos Aires, and now the pope.

What Bergoglio said at a meeting they scheduled soon afterward was even more surprising, after months of public criticisms from church officials of a push to legalize same-sex marriage in the South American country.

"He told me. ... 'I'm in favor of gay rights and in any case, I also favor civil unions for homosexuals, but I believe that Argentina is not yet ready for a gay marriage law,'" said Marquez, a gay rights activist, a self-described devout Catholic and a former theology professor at a Catholic seminary.

As archbishop of Buenos Aires, Bergoglio was one of the leaders of the Catholic Church's public charge against legalizing same-sex marriage in Argentina. He engaged in a notorious war of words with the government of President Cristina Fernandez de Kirchner, which supported the measure.