VATICAN CITY (CNS) -- Appealing on behalf of the world's migrants, Pope Benedict XVI said Christians should put their faith into action and give priority attention to refugees and immigrants.

The pope said St. Paul -- a "missionary to migrants" -- should inspire Christians to show solidarity with the diverse world of today's migrants, including the "victims of modern forms of slavery" and human trafficking.

The pope made the comments in his annual message for the World Day for Migrants and Refugees, which will be celebrated Jan. 18. The papal text was released at the Vatican Oct. 8.

The pope's theme, "St. Paul: Migrant, Apostle of the Peoples," echoed the current jubilee year dedicated to the 2,000th anniversary of the saint's birth.

Traveling far and wide, St. Paul made himself an ambassador-at-large for Christ and a "migrant by vocation," the pope said. In doing so, the saint understood the hardships of migrants and the importance of taking the Gospel to the most diverse populations, the pope said.

St. Paul thus anticipated the church's mission in the modern age of globalization, a mission aimed at the many groups of migrants: students far from home, displaced people, immigrants, refugees, evacuees and those exploited in human trafficking, the pope said.

He said St. Paul's letters present a model of a church that "was not exclusive but on the contrary open to all, formed by believers without distinction of culture or race."

This model also was based on fraternal solidarity expressed in "daily gestures of sharing," demonstrating that the Gospel must be listened to, welcomed and lived, he said.

If Christians understand this, they cannot fail to show special concern for refugees and the displaced, the pope said.

"How can we fail to meet the needs of those who are de facto the weakest and most defenseless, marked by precariousness and insecurity, marginalized and often excluded by society?" he said.

The church should give its priority attention to them, the pope said, citing St. Paul's words in his First Letter to the Corinthians that "God chose what is weak in the world to shame the strong."

He said the church's celebration of the annual migrant day should help its members "live brotherly love to the full without making any kind of distinction and without discrimination," remembering that "anyone who needs us and whom we can help is our neighbor."

St. Paul's example helps people understand that "the exercise of charity is the culmination and synthesis of the whole of Christian life," he said.

At a Vatican press conference, Cardinal Renato Martino, president of the Pontifical Council for Migrants and Travelers, said there were more than 200 million migrants in the world, many of them driven from their homelands by war, famine or economic necessity.

The phenomenon has shown itself to be unstoppable, and has prompted a "climate of closure" in some richer countries, the cardinal said. He said the proper response was not for countries to close their borders, but to welcome immigrants with balanced and fair regulation.

Archbishop Agostino Marchetto, secretary of the pontifical council, said new measures aimed at keeping immigrants out of richer countries have led to an "erosion of humanitarian standards." He criticized the publication of lists of "safe countries" of origin when dealing with asylum seekers.

© 2008 Catholic News Service/U.S. Conference of Catholic Bishops