Pope Francis returned from a brief respite on Saturday, receiving the Madagascan president and delegates from the Orthodox Church after a "sudden indisposition" forced him to cancel a visit a day earlier.
Witnesses said the pontiff, who is aged 77, seemed tired but was smiling as he entertained his guests.
The day before, he had cancelled a trip to a hospital in Rome at the last minute, with a spokesman mentioning "the intense pace" of the pope's schedule by way of explanation.
"With so many undertakings, it's clear there's a need for a break every now and then," Vatican spokesman Federico Lombardi told AFP.
The usually energetic pope gets up at five o'clock every morning, and often has a full day of religious and diplomatic engagements.
Local media reported that the pope was "very tired" and suffering from a headache made worse by a recent heat wave.
His condition improving by Saturday, he received the Canadian Cardinal Marc Ouellet, the prefect of the Congregation of Bishops, at 0730 GMT before meeting the Madagascan President Hery Rajaonarimampianina to discuss the fight against poverty.
The pope also gave a speech in front of a delegation representing the Orthodox Patriarch of Constantinople, Bartholomew I, who the pope called his "beloved brother."
AFP, photo by Christus Vincit