said on Saturday the decades-long abuse of Indigenous schoolchildren across amounted to "genocide" as he returned from a six-day trip with an acknowledgement that he needed to slow down his pace of travel – or could even resign.
During his "penitential pilgrimage" across Canada this week, the 85-year-old offered a historic apology to the First Nations, Métis and Inuit people for what he called the "evil" committed at Catholic-run residential schools.
Speaking to reporters on his return home, the head of the world's 1.3 billion Catholics used the word "genocide" to describe the treatment of children wrenched from their families and cultures to attend the state schools.
While he told reporters the word "didn't come to my mind" while in Canada, "I did describe the genocide. And I asked for forgiveness for this process which was genocide".
"Taking away children, changing the culture, changing the mentality, changing the traditions, changing a race, let's put it that way, a whole culture," he said.
Although Francis's unprecedented apology was mostly welcomed across Canada, from western Alberta to Quebec and the far north, many survivors said much more needed to be done for reconciliation.
Canada was the pope's 37th international trip since he was elected in 2013, but he admitted he would have to slow down his pace due to knee problems that saw him spent much of the visit in a wheelchair.
"I think that at my age and with this limitation, I have to save myself a little bit to be able to serve the Church. Or, alternatively, to think about the possibility of stepping aside," the pope said.
It was not the first time Francis has said that, if required, he could follow his predecessor Benedict XVI, who made history in 2013 by resigning due to his own declining health.
"The door is open, it's one of the normal options, but up until now I haven't knocked on this door," he said on Saturday.
"But that doesn't mean the day after tomorrow I don't start thinking, right? But right now I honestly don't."
His comments will fuel already intense speculation about the pope's future, after he cancelled a string of events in recent months, including a long-planned trip to South Sudan and the Democratic Republic of Congo.
Ruling out surgery due to the risks of anaesthesia at his age, the pope – who underwent colon surgery last year – said he still planned to travel to Kazakhstan in September, and still had hopes of a trip one day to war-torn Ukraine.
He had wrapped up his Canadian journey on Friday in the capital of the vast northern territory of Nunavut, Iqaluit, again asking forgiveness for abuse committed at the 139 residential schools run by the Catholic Church.
About 150,000 Indigenous children were sent there from the late 1800s to the 1990s.
"I want to tell you how very sorry I am and to ask for forgiveness for the evil perpetrated by not a few Catholics who contributed to the policies of cultural assimilation," he said.
Many children were physically and sexually abused at the schools, and thousands are believed to have died of disease, malnutrition or neglect, in what a truth and reconciliation commission later called a "cultural genocide".
Residents in Iqaluit, a community of just over 7,000 people and where small houses line the rocky ocean shore, have listened closely to the pope's words throughout his trip.
"He did apologise, and a lot of people don't seem to be happy with it, but he took that step to come to Nunavut… and I think that's big," lifelong Iqaluit resident Evie Kunuk, 47, told AFP.
Throughout the trip, Indigenous people have spoken of a "release of emotion" at hearing the pope's words, while warning it was only the beginning.
Many have observed that he did not specifically mention or apologise for the sexual abuse committed at the schools, despite the scandal over such abuse of children by Catholic clergy the world over.
Some called for Francis to rescind the Doctrine of Discovery, the 15th-century papal bulls that allowed European powers to colonise any non-Christian lands and people.
"This doctrine of colonisation, it's true, it's bad, it's unfair," he said on Saturday, adding that "there has always been a danger, a mentality of 'we are superior and these indigenous people don't matter', and that is serious".
He said it was necessary to "go back and clean up everything that was done wrong, but with the awareness that today there is the same colonialism", he said, citing the case of the Rohingyas in Myanmar.
Demands were also made in for access to records documenting what happened in the schools, and for the Vatican museums to return Indigenous artefacts.