When Prime Minister Stephen Harper meets with Pope Benedict XVI this weekend, it will be a rare opportunity for an audience with the man who leads the billion-strong flock of worldwide Catholics.

But the visit also comes with a set of expectations for those who meet face to face with the 82-year-old Catholic pontiff, and a set of protocols they must follow when meeting with him privately, as the prime minister will do on Saturday morning.

Michael Higgins, a Vatican affairs specialist at St. Thomas University, said a face-to-face visit with Pope Benedict involves following the strict rules of Vatican protocol, which has been developed over centuries.

There are different rules depending on the reason and purpose of the visit, as well as for the type of visitors who will be speaking with the pope.

In Harper's case, he will be visiting the Vatican as the Canadian prime minister, Higgins said, which entails a different protocol than if he were the country's head of state.

"The nature of the visit will define what protocol applies under those circumstances," Higgins told CTV.ca in a recent phone interview from Fredericton.

Harper's first-ever meeting with the pope -- the first for a Canadian prime minister since 2002 -- will come at a time when the pope has visited with several world leaders who took part in the recent G8 summit meeting in nearby L'Aquila, Italy.

"It would be publicly discourteous for a leader not to pay a visit to the head of the Vatican city state," Higgins said, pointing to other G8 leaders, including U.S. President Barack Obama, who will visit the pontiff before the end of the weekend.

For that reason, Harper's visit will be with the pope's role as head of Vatican City, rather than as a spiritual leader, Higgins said.

Father Thomas Rosica, a Toronto-based Vatican watcher, said that the type of private visit that Harper will have with Pope Benedict is typically arranged at least a month in advance.

"Normally, the pope would be up in the mountains right now on vacation," Rosica told CTV.ca in a recent phone interview from Toronto. "But I think he stuck around because he knew all the G8 people were stopping by."

When Harper arrives at the Vatican, he will be expected to dress formally, with a dark suit being a likely choice, Rosica said, and his meeting with Pope Benedict will take place in the pontiff's office.

"It takes place in his formal office, the receiving office," Rosica said. "They would both be seated."

Following a formal greeting, pictures are taken and a gift is generally given to the visiting dignitary -- and usually a reciprocal gift is given to the pope.

So far this week, the pope has received six bottles of wine from Australian Prime Minister Kevin Rudd and a digital video recorder from Japanese Prime Minister Taro Aso. It is not known what gift Harper will bring for Pope Benedict.

After the formalities, the prime minister and pope will have a private chat -- and although some aides might be present, the contents of the conversation will not be reported.

The two men will likely chat for between 15 minutes to a half hour, Higgins said, and Pope Benedict might even talk about his prior visits to Canada -- back when the pope was still known as Cardinal Joseph Ratzinger.

"At the end of it, the pope rings the little buzzer that is on his desk, and his assistant comes in and brings in the rest of the people," Rosica said.

Following the private portion of the meeting, there could also be an exchange of speeches between Harper and the pope, in which case, the remarks would be released to the public.

Images of the meeting will be recorded and distributed by the Vatican press office, Rosica said.

It remains to be seen whether Harper will be nervous when meeting the pope, days after being accused of pocketing a communion wafer at a memorial service in New Brunswick - something the prime minister has said did not happen.

On Friday, Harper criticized reporters who ran the "terrible" communion story for being responsible for "a low moment in journalism."

Background on Canada and the Vatican

Harper will be the first Canadian prime minister to visit with Pope Benedict, who became pontiff nearly four years ago.

Paul Martin did not meet with the pope during his tenure as prime minister, though he did attend the funeral of pope John Paul II in April 2005.

While Jean Chretien served as prime minister, he met pope John Paul II on four occasions, in Toronto in July 2002, and at the Vatican in May 1998, June 1996 and July 1994.

Former prime minister Brian Mulroney met with John Paul II at the Vatican in January 1987 and before that in Ottawa in September 1984.

The late prime minister Pierre Trudeau met with pope Paul VI on two occasions at the Vatican, first in January 1969 and again in March 1975. His first meeting with the pope led to Canada opening diplomatic relations with the Vatican, which happened on Oct. 15, 1969.

In Ottawa, the envoy to the Vatican lives in a French chateau worth $14.7 million, recently rated by the Ottawa Business Journal as the second-most expensive diplomatic residence in Canada's capital city.