WASHINGTON (CBSDC/AP) — An FBI official says “it is all hands on deck” as Pope Francis begins his historic visit to the United States Tuesday afternoon.

CBS News reports that some are calling the pope’s visit the “largest security operation in U.S. history.”

“It is all hands on deck,” Paul Abbate, head of the FBI Washington Field Office, tells CBS News. “I would say it’s one of the largest, if not the largest special event we’ve ever seen here.”

There have been no credible threats against the pope, but CBS News reports that Pennsylvania State Police warned of people impersonating police officers to carry out attacks ahead of the pope’s visit.

The Secret Service has been studying the pope’s movement for months and also has access to a 3-D virtual map to get an advanced look at where he will visit.

“No one can say with 100 percent certainty that you can stop everything, but there are steps you can take to minimize any opportunity for anyone to commit any kind of acts,” Philadelphia Police Commissioner Charles Ramsey explained to CBS News.

The pope will fly from Cuba and land in Washington, D.C., Tuesday afternoon where he will be greeted by President and Mrs. Obama. He will also make his way to New York and Philadelphia during his U.S. stay.

The pope held Mass at Cuba’s holiest shrine – the Sanctuary of the Virgin of Charity of El Cobre – Tuesday morning, which was attended by Cuban President Raul Castro.

Francis  called on Cubans to rediscover their Catholic heritage and live a “revolution of tenderness,” highly evocative words in a country whose 1959 revolution installed an atheist, Communist government that sought to replace the church as the guiding force in people’s lives.

The pope said that “our revolution comes about through tenderness, through the joy which always becomes closeness and compassion, which isn’t pain, and leads us to get involved in, and to serve, the life of others.”

Francis has been carefully balancing his desire to work with Castro’s government on its path of internal reform and detente with the United States with his longstanding critiques of Communism as a system that stifles the spirit.

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