VATICAN CITY (CNS) -- With world peace under serious threat, Pope Francis called on all nations to observe the Olympic truce and cease all conflicts for the traditional period before, during and after the Olympic Games in Paris.

"As is the custom of this ancient tradition, may the Olympic Games be an occasion to call for a cease-fire in wars, demonstrating a sincere desire for peace," he said after praying the Angelus with visitors gathered in St. Peter's Square July 21.

"I hope that this event may be a beacon of the inclusive world we want to build and that athletes, with their sporting testimony, may be messengers of peace and authentic models for young people," he said.

The pope's appeal came after he sent a written message to Archbishop Laurent Ulrich of Paris, who celebrated Mass at the Church of Sainte-Marie-Madeleine in Paris July 19 to mark the official start of the Olympic truce.

May God help "enlighten the consciences of those in power to the grave responsibilities incumbent upon them, may he grant peacemakers success in their endeavors," the pope said in the letter that the Vatican published July 19, seven days before the opening of the Summer Games and the customary start of the observance of the Olympic truce.

The Olympic truce tradition, originating in Greece in the 8th-century B.C., asked that all wars and conflict be suspended during the games and seven days before and after the games as a way to make sure participants could travel to and from the venue safely.

The International Olympic Committee revived the tradition in 1992 and it works with the United Nations to pass a symbolic U.N. resolution before each Games inviting U.N. member states to observe a truce to encourage the Olympic spirit of peace.

In his letter, the pope said the Olympic Games can be "an exceptional meeting place between peoples, even the most hostile. The five interlinked rings represent the spirit of fraternity that should characterize the Olympic event and sporting competition in general."

"I therefore hope that the Paris Olympics will be an unmissable opportunity for all those who come from around the world to discover and appreciate each other, to break down prejudices, to foster esteem where there is contempt and mistrust, and friendship where there is hatred. The Olympic Games are, by their very nature, about peace, not war," he wrote.

"It was in this spirit that antiquity wisely instituted a truce during the Games, and that modern times regularly attempt to revive this happy tradition," the pope wrote.

"In these troubled times, when world peace is under serious threat, it is my fervent wish that everyone will take this truce to heart, in the hope of resolving conflicts and restoring harmony," he wrote.

Pope Francis also sent his support and blessings to all athletes, spectators and the people of Paris, including the many Catholics who "are preparing to open wide the doors of their churches, schools and homes."

"I hope that the organization of these Games will provide the people of France with a wonderful opportunity for fraternal harmony, enabling us to transcend differences and opposition and strengthen the unity of the nation," he wrote.

The Olympic Games begin July 26 and run until Aug. 11, followed by the Paralympic Games, which will take place from Aug. 28 to Sept. 8.

Some 10,500 athletes from around the world are set to compete in the Olympics and as many as 4,400 in the Paralympics. Thirty-seven athletes from 11 countries of origin are expected to represent the Refugee Olympic Team at the Summer Games and eight athletes from six countries will compete in the Refugee Paralympic Team.

The Paris Summer Games will mark the first time there is the same number of women and men competing in events since the modern Summer Olympics began in Athens in 1896 and where all the athletes were men.