Pope Francis' killer pace is wearing out his aides.

The 76-year-old Argentine Jesuit, who lost most of one lung following an infection in his youth, has been acting like a man half his age during his first international trip as pope, adding in events at the last minute to his already full schedule and gamely going with the flow after heavy rains forced major changes in the World Youth Day agenda.

His spokesman, the Rev. Federico Lombardi, noted Thursday that such vigorous activity has been the norm at the Vatican ever since Francis came to town, saying the Vatican's usually staid bureaucrats were getting "stressed out" by his pace _ and that that was a good thing.

But he quipped: "I'm happy we're half-way through because if it were any longer I'd be destroyed."

Francis added two unscheduled events Thursday to an already full day: a morning Mass with some 300 seminarians from the region, and then a meeting at Rio's cathedral with some 30,000 Argentine pilgrims.

Asked when Francis would actually return to his home country, Lombardi revealed that there were no plans for a trip to Argentina in 2014 as had been widely expected.

Rather, he said, the pope planned to visit another continent given he had already been to Brazil in 2013 and, as he announced somewhat unexpectedly on Wednesday, would be returning in 2017 to mark the 300th anniversary of the discovery of the statue of the Virgin of Aparecida, Brazil's patron saint.

Lombardi didn't say which continent might get a papal visit in 2014, but mentioned Africa, Asia or the Holy Land as possibilities.