The pontiff's condition is touch-and-go, given his age, fragility and pre-existing lung disease, according to doctors.

The Vatican described his condition as critical for the first time on Saturday, reporting that the 88-year-old Francis needed supplemental oxygen and blood transfusions after a "prolonged asthma-like respiratory crisis.

Pope Francis remains in critical condition, according to the Vatican, with blood tests showing mild signs of kidney failure “which is currently under control,” the Vatican said Sunday, as the 88-year-old pontiff battles pneumonia in both his lungs.