By Philip Pullella and Joanna Zuckerman Bernstein
SAN CRISTOBAL DE LAS CASAS, Mexico (Reuters) - Pope Francis travels on Monday to Mexico's poor, indigenous south, which has fallen far behind wealthier parts of the country and where he will authorize the use of native languages for Mass in a bid to stem a tide of Protestant conversions.
Mired in poverty and plagued by rising insecurity, the state of Chiapas was the scene of the Zapatista uprising of Maya rebels in the 1990s. It is now the frontline of a government crackdown on illegal immigration to the United States from Central America.
When the Zapatistas burst onto the scene, more than two thirds of Chiapas' population was Roman Catholic. The expansion of evangelical Christianity through poor indigenous towns since has driven the number down to around 60 percent, making it Mexico's least Catholic region.
In the colonial mountain city of San Cristobal de las Casas, the pope will visit the church that houses the tomb of Samuel Ruiz, who was a champion for indigenous rights and served as a mediator between the Zapatistas and the government.
Ruiz, who died in 2011, long lobbied to permit Mass in languages such as Tzotzil because many of the region's Maya residents do not speak Spanish.
Before dawn on Monday, people gathered along the road outside a sports stadium in San Cristobal where the pope will celebrate Mass, many women in indigenous dress of black skirts and colorful tops, their hair braided with ribbons.
"He is bringing a message for us to ... become Catholic again," said Rocío Roman, 58, a local bank manager. "San Cristobal used to be more Catholic, but many people, mostly indigenous, have converted to other religions."
The pope last year apologized for the role of the Church in the conquest of Latin America and he is expected to issue a decree while in Chiapas to authorize translations of the liturgy.
Francis is visiting some of the most marginalized parts of Mexico. On Sunday, he took a swipe at the its rich and corrupt elite in a Mass near the cinder block slums of Ecatepec, one of the country's most violent cities.
The poverty rate in Chiapas, already the most impoverished state in Mexico, has risen in recent years to more than three-quarters of the population.
President Enrique Pena Nieto last year launched a plan to boost the economy of the south by building more infrastructure. Previous development plans have failed, crippled by waste and corruption.
Mexico, with help from the United States, has increased patrols on its southern border and is deporting more Central American migrants trying to reach the United States.
Francis may highlight the struggle of Central American migrants during his visit. He will also meet indigenous leaders and hold a stadium rally in the capital of Tuxtla Gutierrez.
Thousands of people from neighboring Guatemala are believed to have crossed over the porous border of rivers and jungle in Chiapas for a chance to see the pope.
On Tuesday, he will speak to youths in Morelia, the capital of Michoacan state, where warring drug gangs cook much of the methamphetamine smuggled into the United States.
He will then travel to Ciudad Juarez, across from the U.S. border, where he will pray for migrants and victims of violence.
(Writing by Michael O'Boyle; Editing by Frank Jack Daniel and Kieran Murray)