ROME -- Pope Francis on Saturday praised the zeal of an 18th-century Franciscan missionary he will make a saint when he visits the United States this fall but whom Native Americans contend brutally converted indigenous people to Christianity.

Francis praised Junipero Serra during a homily at a Rome seminary training future priests from North America. The pope will proclaim the Spaniard a saint during a Washington, D.C., ceremony Sept. 23.

Native Americans have protested in California, saying the friar should be criticized for what they contend is his role in wiping out native populations in a brutal campaign to impose Catholicism. They contend he enslaved converts.

Francis described Serra as part of a missionary corps who "went out to all the geographical, social and existential peripheries" to spread the Gospel.

"Such zeal excites us," Francis said.

Without wading into specific criticisms of Serra, Francis said of these missionaries: "Sometimes we stop and thoughtfully examine their strengths and, above all, their weaknesses and shortcomings."

The soon-to-be saint helped defend "the indigenous peoples against abuses by the coloniziers," Francis contended.

The church's first Latin American pope expressed a kind of awe for the likes of Serra, saying "I wonder if today we are able to respond with the same generosity and courage" in leaving comfortable lives to proclaim God to those who haven't "experienced the embrace of his mercy."

Serra, who died in 1784, "ushered in a new springtime of evangelization in those immense territories, extending from Florida to California," Francis said. The Vatican sees Serra as a role model for the growing U.S. Hispanic Catholic population.

Before celebrating Mass at the seminary with Francis, Washington Cardinal Donald Wuerl dismissed concerns that canonizing Serra could be a divisive act offending Native Americans.

"The message of the Holy Father is reconciliation," Wuerl said.