ROME - The joint sanctification of Popes John Paul II and John XXIII is expected to draw up to one million pilgrims and tourists to Rome this weekend, authorities said Wednesday.

John Paul II, born in Poland as Karol Wojtyla, led the Catholic Church from 1978 to 2005, while John XXIII, born Angelo Roncalli in Italy, presided from 1958 to 1963. Both are hugely popular figures among the faithful.

"We expect a minimum of 500,000 and a maximum of one million people," Maurizio Pucci, an adviser to Rome Mayor Ignazio Marino, told reporters.

"From an organizational point of view, we are prepared for up to 800,000 arrivals," added Msgr. Liberio Andreatta, who is organizing the event on behalf of the Vatican. "We will see if more people come."

Dozens of world leaders are expected to attend the canonization Mass that Pope Francis is to celebrate in St. Peter's Square on Sunday.

Andreatta said 1.2 million picture cards of the soon-to-be-saints had been prepared for the crowds, who will be spread out among the Vatican, its surroundings, and other major public spaces in the Italian capital.

An extra 2,400 police, 2,000 traffic wardens, 1,000 street cleaners, 3,000 volunteers, and hundreds of medical staff have been recruited for the event, which will cost the city more than $7 million, Pucci said.

For its part, the Catholic Church of Rome expects to spend about $700,000 on putting up giant TV screens and other items, Andreatta said. Private sponsors are expected to pick up most of the bill, he added.

On Sunday, 5,000 priests will be deployed in the streets to help out pilgrims.

The simultaneous canonization of two pontiffs is unprecedented in the Catholic Church's history. The last pope to have been recognized as a saint was Pius X, who ruled from 1903 to 1914, in 1954.