By Daniel Becerril

MONTERREY, Mexico (Reuters) - On the troubled fringes of the northern Mexican city of Monterrey, an aspiring Catholic priest is using his faith to reach out to young gang members and at-risk youth and bring them into his "Gang of Christ."

Less than 200 kilometers (125 miles) from the U.S. border, Monterrey is a wealthy city of corporate trailblazers. But violence is never far away on the outskirts, where bricklayers and factory workers walk poorly lit streets to reach simple cinder-block homes.

Jose Luis Guerra, 34, also walks those pathways, searching for young gang members who might listen to his message.

It is a risky vocation: although violence in Monterrey has fallen from the bloody peaks of 2011, an unknown man pacing the streets after dark still risks being seen as a threat.

"My alba is my shield," Guerra says, referring to his white religious robes.

Sometimes seen in his Superman-logo baseball cap, Guerra is a deacon, and will be ordained as a priest in mid-August.

Guerra bumps fists with the young boys and girls he meets, and when he talks to them, he sounds more like a psychologist than a priest. Given to cracking jokes, he says of his considerable girth: "It just means that I am full of love."

Often he visits the back streets with some of his 15 fellow missionaries, two-thirds of whom are ex-gang members themselves.

Becoming a missionary means renouncing not necessarily the gang, but acts that Guerra says devalue people as human beings: theft, assault, insult and, in some cases, murder.

This is followed by three days at 'camp' where candidates must reflect on their lives and commitment to Christ; then, seven weeks at missionary school and finally, upon graduation, a party complete with cumbia dance music.

The official ceremony takes place in a public square, where Guerra explains the responsibilities that come with the job, then presents a Bible to the kneeling subjects.

A few weeks must pass before the newly minted missionaries can begin visiting neighborhoods. First Guerra and the others must tell local gangs the new recruits are no longer their enemies. Instead, he says, they are now members of the "Gang of Christ."

(Writing by Alizeh Kohari; Editing by James Dalgleish)