France, Sept. 25 -- Pope Leo arrives in France on Friday for a four-day state visit that will take him from Paris to Lourdes and Metz on a programme that mixes diplomacy with public worship.

No pontiff has made a state trip to France since Benedict XVI in 2008. The visit is the first by Leo, the only American pope, whose paternal grandmother was born in France.

Preparations are already well underway in central Paris, where a giant white canopy has been erected on the Place de la Concorde ahead of an open-air mass on Saturday. Around 600,000 people have signed up to attend.

The interest reflects the enduring presence of Catholicism in France, even as regular church attendance has fallen.

Only around 5 percent of France's 69 million res...