Pope Francis has cast himself as the spiritual and political leader of the world's oppressed with his remarkable mea culpa for the sins and crimes of the Catholic Church against the indigenous peoples during the colonial conquest of the Americas.

He'll have a chance to embellish that reputation Friday when he visits Bolivia's notorious Palmasola prison.

Francis "humbly" begged forgiveness Thursday at a gathering of indigenous leaders in Bolivia in the presence of Bolivia's first-ever indigenous president, Evo Morales, the climactic high of Francis' weeklong South American tour.

In the speech, Francis noted that Latin American church leaders in the past had acknowledged that "grave sins were committed against the native peoples of America in the name of God." St. John Paul II, for his part, apologized to the continent's indigenous for the "pain and suffering" caused during the 500 years of the church's presence in the Americas during a 1992 visit to the Dominican Republic.

But Francis went further, and said he was doing so with "regret."

"I would also say, and here I wish to be quite clear, as was St. John Paul II: I humbly ask forgiveness, not only for the offenses of the church herself, but also for crimes committed against the native peoples during the so-called conquest of America," he said to applause from the crowd.

Then deviating from his prepared script, he added: "I also want for us to remember the thousands and thousands of priests who strongly opposed the logic of the sword with the power of the cross. There was sin, and it was plentiful. But we never apologized, so I now ask for forgiveness. But where there was sin, and there was plenty of sin, there was also an abundant grace increased by the men who defended indigenous peoples."

Francis' apology was met with wild applause from the indigenous and other grass-roots groups gathered for a world summit of popular movements whose fight against injustice and social inequality has been championed by the pope.

"We accept the apologies. What more can we expect from a man like Pope Francis?" said Adolfo Chavez, a leader of a lowlands indigenous group. "It's time to turn the page and pitch in to start anew. We indigenous were never lesser beings."

The apology was significant given the controversy that has erupted in the United States over Francis' planned canonization of the 18th century Spanish priest Junipero Serra, who set up missions across California. Native Americans contend Serra brutally converted indigenous people to Christianity, wiping out villages in the process, and have opposed his canonization. The Vatican insists Serra defended natives from colonial abuses.

Francis' apology was also significant given the controversy that blew up the last time a pope visited the continent. Benedict XVI drew heated criticism when, during a 2007 visit to Brazil, he defended the church's campaign to Christianize indigenous peoples. He said the Indians of Latin America had been "silently longing" to become Christians when Spanish and Portuguese conquerors violently took over their lands.

Amid an outcry from indigenous groups, Benedict subsequently acknowledged that "shadows accompanied the work of evangelizing" the continent and said European colonizers inflicted "sufferings and injustices" on indigenous populations. He didn't apologize, however.

The Vatican spokesman, the Rev. Federico Lombardi, said that Francis wrote the speech on his own and that the apology for the sins, offenses and crimes of the church was a "particularly important declaration."

Church officials have long insisted Catholic missionaries protected indigenous peoples from the abuses of military colonizers and were often punished by European colonial powers as a result. Francis' own Jesuit order developed missions across the continent, educating the indigenous and turning their communities into organized Christian-Indian societies. The Jesuits were expelled in the 17th century.

Mexican Bishop Raul Vera, who attended Thursday's conference, said the church was essentially a passive participant in allowing natives to become enslaved under the "encomienda" system, in which Spain's king granted land in conquered territories to those who settled there. Indians were allowed to live on the haciendas as long as they worked them.

"It's evident that the church did not defend against it with all its efforts. It allowed it to be imposed," Vera told The Associated Press before the pope's speech.

During the speech, the longest and most important of Francis' weeklong, three-nation South American trip, the pope touched on some of the priorities of his pontificate, a key one being the need to change what he called an unjust global economic system that excludes the poor. He said it should be replaced with a "communitarian economy" involving the "fitting distribution" of the Earth's resources.

"Working for a just distribution of the fruits of the Earth and human labor is not mere philanthropy. It's a moral obligation," he said.

Francis ended the speech with a fierce condemnation of the world's governments for what he said was "cowardice" in defending the planet. Echoing his environmental encyclical of last month, the pope said the Earth "is being pillaged, laid waste and harmed with impunity" while "one international summit after another takes place without any significant result."

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Associated Press writers Paola Flores, Frank Bajak, Jacobo Garcia and Carlos Valdez contributed to this report.

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Nicole Winfield on Twitter: at www.twitter.com/nwinfield