VATICAN CITY -- Pope Benedict XVI has put the Catholic Church on notice: Social networking sites aren't a virtual world the church can ignore, but rather a very real world that its leaders must engage if they want to spread the faith to the next generation.

The 85-year-old Benedict, who tweets in nine languages, used his annual message on social communications Thursday to stress the potential of social media for the church as it struggles to keep followers and attract new ones amid religious apathy, competition from other churches and scandals that have driven the faithful away.

Archbishop Claudio Maria Celli, head of the Vatican's communications office, cited a 2012 study commissioned by U.S. bishops that found that 53 per cent of Americans were unaware of any significant presence of the Catholic Church online.