Mexico:
- The world's largest Spanish-speaking Catholic country
- Approximately 46% of people live in poverty, including 10% who live in extreme poverty*
- Estimated 100,000 people have been killed in gangland violence since late-2006
*Government statistics
The service is to take place in Ecatepec at a field with an estimated capacity of 400,000 and the Pontiff is expected to bring a message of hope and solidarity to guests.
Since former Mexican President, Felipe de Jesús Calderón Hinojosa, launched a crackdown on drug cartels in late-2006, it's estimated 100,000 have been killed and 27,000 have disappeared in gangland violence.
Francis was described as looking "tired" and "winded" during a gruelling schedule on Saturday which included an evening Mass service in the evening.
The Roman Catholic leader has already used his tour of Mexico to call upon public officials not to be swayed by corruption but to be honest.
He also urged church leaders to help Mexicans "finally escape the raging waters that drown so many, either victims of the drug trade or those who stand before God with their hands drenched in blood, though with pockets filled with sordid money and their consciences deadened".
Francis yesterday also visited the Basilica of the Virgin of Guadalupe, the largest and most important Marian shrine in the world.
Pictures: Pope Francis in Mexico City on Saturday.