Pope Francis will be discharged from Rome's Gemelli hospital on Sunday and will need at least two months of rest at the Vatican, doctors treating him have said.

The 88-year-old was admitted to the hospital on 14 February with a severe respiratory infection that resulted in double pneumonia.

During the past five weeks, he presented "two very critical episodes" where his "life was in danger", Dr Sergio Alfieri, one of the doctors treating the Pope, said.

Pope Francis was never intubated and always remained alert and oriented, Dr Alfieri said. The Pope is not completely healed, but no longer has pneumonia and is now in a stable condition, according to his doctors.

"Today we are happy to say that tomorrow he will be at home," Dr Alfieri told reporters on Saturday.

The Pope will offer a blessing from his window at the Gemelli hospital on Sunday - the first time he will appear in public since he was admitted to hospital - before returning to his residence at the Vatican.

Dr Alfieri said that patients with double pneumonia lose their voice a little and "especially in the elderly, it will take time for your voice to return to normal".

On Friday, Cardinal Victor Fernandez had said "high-flow oxygen dries everything out" and as a result the Pope "needs to relearn how to speak", Reuters had reported.

If the trend of improvement continues, doctors said, the Pope would be able to return to work as soon as possible.

The Vatican had said on Friday that the Pope had seen some improvements in his breathing and mobility.

It had confirmed he no longer uses mechanical ventilation for breathing at night, but was instead receiving oxygen via a small tube under his nose. During the day, he is using less high-flow oxygen.

The Pope has only been seen by the public once since he was admitted to hospital, in a photograph released by the Vatican last week, which showed him praying in a hospital chapel.

Earlier this month, an audio recording of Pope Francis speaking in his native Spanish was played in St Peter's Square in Vatican City.

His voice was breathless as he thanked the Catholic faithful for their prayers.

Pope Francis has spent nearly 12 years as leader of the Roman Catholic Church.

He has suffered a number of health issues throughout his life, including having part of one of his lungs removed at age 21, making him more prone to infections.