Pope Francis skipped reading a planned speech at a conference on Thursday, saying he still had breathing problems following a hernia operation this month.
"I am still under the effects of anaesthesia, my breathing is not good," Francis told a meeting of the Catholic Oriental Church, saying delegates would instead receive a text of the speech.
Asked by a well-wisher how he felt, the 86-year-old pope replied: "I'm still alive."
The pope had surgery on June 7 to repair an abdominal hernia. He spent nine days in hospital recovering and has had a busy schedule since returning to the Vatican last Friday, including meeting the presidents of Cuba and Brazil.
He had eight events on his schedule for Thursday.
The pontiff gave reassurances about his health in a video about his upcoming trip to Portugal from Aug. 2 to Aug. 6 for World Youth Day and to visit the Shrine of Fatima.
"The doctor told me I can travel," Francis said in a message on the Vatican News website.
"There are 40 days left, like Lent, before the meeting in Lisbon. I'm ready! I already have everything, I can't wait to go!" said Francis, brandishing a grey bag with the kit that will be handed out to pilgrims.