What will happen at the Vatican when Trump meets Pope Francis?

Papal visits with heads of state are carefully arranged bits of political and religious theater. They follow a specific and routine schedule, with little room for deviation or unwanted surprises.

While the royalty, president or prime minister making the trip to the Vatican may fret the details, sending teams months in advance to plan out each moment, the city-state's objectives are clear: protect the pope's image and influence, and then fade into the background to let the pope handle the meeting as he wants.

As Ken Hackett, the most recent U.S. ambassador to the Holy See, said in a recent interview: "From the Vatican's point of view, it's pretty normal fare for them to deal with heads of state. They've been doing it for centuries. They know exactly what they will do and can do."

When U.S. President Donald Trump arrives to meet Pope Francis on the morning of May 24, he will be escorted through a series of rooms in the apostolic palace meant to impress upon him the Vatican's historic power and majesty. As he walks, he will pass Swiss Guards in full regalia, standing at attention holding long pole weapons known as halberds.

One of the last rooms the president will enter before meeting the pope is the Sala Ambrogio, named for the third century saint and bishop, and distinctive for its decorate Renaissance-era triptych of Christ's death and resurrection and for containing a large rug decorated with the coat of arms of Pope Leo XIII.

Francis and Trump will meet first briefly in the antechamber of the papal library, where the pope hosts all his formal encounters with heads of state. The two will shake hands there, where a small pool of about five photographers and two print journalists may be able to hear their first words to each other.

Francis will then escort Trump into the library itself, where the two will sit at a large wooden desk across from each other. The journalists are allowed to remain present for the very beginning of the encounter, able to note the details: Is the pope leaning forward in his chair, engaged in the conversation? Are his hands folded, or is gesturing with them? Is he smiling?

After about 30 seconds, everyone but the president, the pope and a translator will be escorted out of the room. No one else will be present for the conversation to follow, meaning no one else can say what happened in the room.

Waiting in another small antechamber, the journalists will begin marking minutes in order to be able to note the exact time, down to the second, that the two leaders spend in private conversation.

A normal meeting is between 20-30 minutes. President Barack Obama, known to have worked well with Francis, spent more than 50 minutes with the pontiff in their March 2014 meeting. Former Canadian Prime Minister Stephen Harper, not known to have enjoyed such a relationship, had less than 10 minutes in June 2015.

Once the private encounter is over, the journalists will be ushered back into the library to witness the formal exchange of gifts between Francis and Trump.

At that point, Trump's entourage — likely to include First Lady Melania, daughter Ivanka, and son-in-law/aide-de-camp Jared Kushner — will also be allowed in and presented one-by-one to greet the pope, each having a short moment with the pontiff to shake his hand and receive a rosary blessed by him.

The pope and president will then walk towards a small table together, where the gifts will be laid out for presentation. Francis normally gives heads of state copies of his three major writings: Evangelii Gaudium, Laudato Si', and Amoris Laetitia.

The pope also normally gives political leaders a medallion of some-sort, which is usually imbued with a specific message. In his March meeting with Myanmar's Aung San Suu Kyi, for example, Francis gave her a 7.5-inch-wide bronze medallion showing a desert turning to bloom in a depiction of the Old Testament prophet Isaiah's words: "The wilderness will become a fruitful field."

"The dry, thorny branch that blossoms and bears fruit symbolizes the passage from selfishness to sharing, from war to peace," the Vatican said in an explanation of that piece, interpreted as a message from the pope about Myanmar's continuing process of democratic reform following a half-century of military rule.

It's up to Trump and his administration to determine ahead of time what to give Francis. The pope normally appears to appreciate gifts that are simple, or creative.

Obama, for example, gave the pontiff seeds from the White House Garden, later planted at the historic papal retreat in Castel Gandolfo. Samoan Prime Minister Tuilaepa Aiono Sailele Malielegaoi elicited a big smile from Francis in December 2015 when he presented a set of fishing hooks traditionally used by his people.

After the exchange of gifts — which will be another chance for journalists to note the pope's and president's demeanor towards each other as they briefly explain what they are giving — the meeting comes to an end. Francis will briefly greet each member of Trump's entourage again as they walk out of the library, leaving the president for last.

As Trump leaves Francis, he will be escorted again through the apostolic palace into a separate room for meetings with Vatican Secretary of State Cardinal Pietro Parolin and Archbishop Paul Gallagher, the secretary for relations with states.

Hackett said that is normally the meeting where the most serious business takes place.

"There's a difference between the meeting with the Holy Father and the meeting with Cardinal Parolin and Archbishop Gallagher," said the former ambassador, adding that he would advise Trump: "On the geopolitical side of things, keep it with Cardinal Parolin and Gallagher."

After witnessing Trump and Parolin greet each other, the journalists will be escorted out of the apostolic palace and will rush back across St. Peter's Square to the press office to brief their colleagues on what has happened, providing any juicy details of what they could hear the pope and president say.

All will then wait for the Vatican to put out an official statement summarizing the discussions between Trump, Francis, and Parolin. Normally, such statements are brief and bland; no more than a paragraph or two and nothing more specific than describing "cordial conversations" that addressed "various themes of common interest."

Many surely will also be carefully monitoring Trump's Twitter feed, watching for his version of events.

[Joshua J. McElwee is NCR Vatican correspondent. His email address is jmcelwee@ncronline.org. Follow him on Twitter: @joshjmac.]