Pope Francis has cancelled his trip to the COP28 climate summit in Dubai due to influenza and lung inflammation, the Vatican said.
The Pope, 86, was due to begin a three-day visit on Friday.
Earlier on Tuesday, the Vatican had said he planned to go ahead with the trip despite having been ill over the weekend.
The pope had agreed not to travel "with great regret" after being asked not to go by his doctors, it said.
"Although the Holy Father's general clinical condition has improved with regard to the flu and inflammation of the respiratory tract, doctors have asked the pope not to make the trip planned for the coming days to Dubai," the Vatican said.
On Saturday, the Pope cancelled events due to what the Vatican described as "light flu symptoms". He underwent a CT scan which ruled out pneumonia but did show some inflammation.
For his weekly blessing and Sunday message he appeared seated in the chapel of his residence instead of in St Peter's Square, while an aide read his message and a bandage holding an intravenous tube could be seen on his hand.
Pope Francis has had several health issues this year. He was admitted to hospital with bronchitis in March and underwent abdominal surgery on a hernia in June.
In Dubai, the Pope was expected to criticise countries for a lack of action on climate change and seek to persuade them to cut greenhouse gas emissions.
The Vatican said he still wished to be part of the discussions.
The Pope has made the environment a key pillar of his papacy and warned last month the world was "collapsing" due to climate change and may be "nearing breaking point".
World leaders are set to discuss tackling climate change at the big UN summit in the United Arab Emirates from Friday until 12 December.
More than 200 governments are invited along with charities, community groups, think tanks and businesses.
