The 88-year-old head of the Catholic Church was "very happy" to hear his health had improved sufficiently for him to leave the Gemelli Hospital in Rome, one of the doctors, Sergio Alfieri, said Saturday.

But the pontiff, who had part of one lung removed as a young man, still faced a recovery period of "at least two months," Alfieri cautioned.

Pope Francis was expected to be discharged from the hospital in the early afternoon. 

The Vatican said he was to make a blessing and wave at well-wishers outside the hospital shortly beforehand, just after midday local time, in what would be his first public appearance since Feb. 14.

His hospitalisation since that date was the longest of the pope's reign, and the fourth since his election in 2013. 

The increasingly fragile state of his health has spurred speculation about whether Francis could opt to step down and make way for a successor, as his predecessor Benedict XVI had done.

'A period of rest'

The pope's doctors, speaking to reporters at Gemelli Hospital on Saturday, said Francis was doing better. The Vatican on Wednesday had said he was now breathing without having to use an oxygen mask.

But Alfieri said: "Further progress will take place at his home, because a hospital, even if this seems strange, is the worst place to recover because it's where one can contract more infections."

The doctor said that, on Sunday, "the pope will leave and return to Saint Martha's House" in the Vatican, where Francis has his residential suite. However Alfieri dismissed the possibility of Francis quickly getting back to his regular duties.

"Convalescence, by definition, is a period of rest. So it is clear that during the convalescence period he will not be able to take on his daily usual appointments."

Easter question

Questions therefore remain over who might lead the busy schedule of religious events leading up to Easter, the holiest period in the Christian calendar. 

The pope has missed the Angelus prayers, normally recited by the pontiff every Sunday, for five straight weeks.

On Monday, asked by reporters about the speculation of Francis resigning, Vatican Secretary of State Pietro Parolin replied: "No, no, no, absolutely not." 

Catholics and others worldwide have been praying for the pope's speedy recovery. Many have been leaving flowers, candles and notes for Francis outside the Gemelli hospital.

At the most alarming stage of the pope's hospitalisation, he spent several weeks on assisted breathing, with nasal tubes and an oxygen mask. Twice, he went through "very critical" moments during which his life was in danger, but he remained conscious, his doctors said.

He was only declared out of danger after a month of treatment in Gemelli Hospital.

The pneumonia he suffered means that Francis will require physical re-education to recover use of his voice.

"When you suffer bilateral pneumonia, your lungs are damaged and your respiratory muscles are also strained," Alfieri said. "It takes time for the voice to get back to normal."

Although the pope has not made a public appearance since Feb. 14, the Vatican on March 16 published a photo of him praying in a chapel in his hospital room.

On March 6, an audio recording of the pope was released in which, speaking in a weak voice, he thanked the faithful praying for him.