President Cristina Fernandez will travel to the Vatican to attend her fellow Argentine Jorge Bergoglio's first Mass as Pope Francis on March 19, and she sent him a warm congratulations letter despite their profound differences over politics.

Bergoglio and Fernandez clashed so often that his official biographer, Sergio Rubin, compared them to "oil and water." When Bergoglio urged parishioners to join a campaign he called "God's war" against gay marriage, she compared the Argentine church leader's tone to the Middle Ages and the Inquisition. In 2010, Argentina became the first country in Latin America to legalize gay marriage.

But Wednesday night, her spokesman Alfredo Scoccimarro announced that "she's going to the assumption, let there be no doubt."

In her open letter, she expressed to "your Holiness my consideration and respect."