The Vatican has commenced the Roman Catholic Church's campaign against the legalisation of abortion in Mexico.

A senior pro-life cardinal has inaugurated an international anti-abortion conference by giving a mass at the Basilica of the Virgin of Guadalupe, the most important Catholic shrine in the Americas.

Cardinal Alfonso Lopez Trujillo addressed approximately 300 people calling for the strengthening of women to teach their children "moral values".

The campaign may get in trouble with the Mexican government, as the country holds a constitutional ban on any political activities from religious groups, although Cardinal Lopez Trujillo did not specifically speak out against abortion during his address.

Mexico has the second-largest Catholic population in the world, and its President, Felipe Calderon, is also a campaigner against abortion.

Rev Hugo Valdemar, spokesman for the Catholic Archdiocese of Mexico City said, "In the name of Jesus Christ and his Gospel, we ask, we implore they do not approve an unjust and bloody law that kills the innocent," in an AP report.

Cardinal Lopez Trujillo said the number of abortions in the world is already extreme, telling conference delegates that "we don't have a reason to shred a human being who is a creation of God and who carries the world's hope".

The main opposition party in Mexico, the Democratic Revolution Party, who proposed the bills to legalise abortion in the first three months of pregnancy, has asked the church to stay out of the issue.

The bill to legalise abortion is expected to pass easily in Mexico City, where Democratic Revolution holds the mayorship and the majority of seats in the city legislature. However, the proposals are expected to face a tougher battle in the national Senate.

Most Latin American countries, including Mexico, allow abortion if the woman's life is in danger or in cases of rape or incest. In 2006, Nicaragua banned abortion in all cases. The US permits abortions within the first 12 weeks of pregnancy.