Pope Francis stepped right into the heated debate over immigration, celebrating mass just feet from Mexico's border with the U.S. NY1's Michael Scotto filed the following report.

Pope Francis set the tone for his homily without even saying a word. Just moments before celebrating Mass before a crowd of 200,000, the Pope walked up to a cross on the U.S.-Mexico border and laid a bouquet of flowers to remember those who have lost their lives trying to get to the United States.

"Let us together ask our God for the gift of conversion, the gift of tears," Pope Francis said. "No more death nor exploitation. There's always time to change, always a way out, always an opportunity, always time to implore the mercy of God."

His call for compassion during his last Mass in Mexico comes amid a U.S. presidential campaign marked by a harsh debate over immigration. In recent years, thousands of Central American migrants have made the dangerous journey to the U.S. border in an effort to flee terrible poverty and violence.

"So many of these brothers and sisters of ours are the consequence of the traffic in human beings, the trade in people," Pope Francis said. "This human tragedy that is forced migration is a global phenomenon."

Francis, born to Italian immigrants in Argentina, had hoped to cross the border by land when he visited the United States last year, but logistical issues prevented that. Francis did not step foot in the United States during this trip, but tens of thousands gathered at an El Paso, Texas stadium to watch a simulcast of the Mass.

Observers say the pope's visit was aimed at showing solidarity with those who often live in the shadows.

"Clearly, he's made a very, very important part of his papacy the place of migrants, the importance and their dignity," said Monsignor Kevin Sullivan, executive director of Catholic Charities of New York.  

A message of dignity was also on display when Francis visited a Mexican prison shortly before he made his emotional trip to the border.