The pope asked an aide to read his speech for him at his weekly audience in the Vatican on Wednesday, with the 86-year-old “not well” enough.
He then stood up from his chair in the Vatican’s auditorium to give his blessing, and with a voice barely above a whisper he said “since I am not well” his reading would not sound “pretty”.
The pope then handed his printed speech to the aide – but he did speak at the end of the audience to voice support for the truce between Israel and Hamas.
He added he hopes “all the hostages are released and access necessary to permit humanitarian aid” to reach Gaza is provided.
“They lack bread, water, the people are suffering,” Pope Francis said.
Doctors had asked the pope – who had part of one lung removed as a young man and has a lung inflammation causing breathing problems – to cancel his trip to COP28.
The Vatican says his condition has improved, but noted he had the flu and “inflammation of the respiratory airways”.
According to the Holy See, the pope still wants to participate in the discussions in some way.
Towards the end of Wednesday’s audience, circus performers came on stage to entertain him with an acrobatic act.
“I want to say thanks for this moment of joy,” Pope Francis said, adding the circus expresses the human dimension of “simple joy”.
He was taken to hospital earlier this year for three days for intravenous treatment with antibiotics of what the Vatican then said was bronchitis.
A CT scan, performed at a Rome hospital on 25 November, had ruled out pneumonia, according to the Vatican.