The three-time World Cup winner, regarded among the greatest players of all time, underwent surgery to remove a tumour from his colon last year, and has been in and out of hospital since.
He was hospitalised earlier this week, though his daughter said there was "no surprise or emergency", with Pele then saying it was a "monthly visit" in a post on Instagram.
However, a report in Folha de Sao Paulo on Sunday (AEDT) said Pele was no longer responding to chemotherapy treatment and is now receiving pain-relieving measures in a palliative end-of-life care ward.
The 82 year old will not be the subject of any invasive treatment or tests.
As a teenager, Pele inspired Brazil to its first World Cup triumph in 1958 and won the tournament with the Selecao twice more in 1962 and 1970.
Last week, when Brazil got its 2022 campaign under way, he sent a message of good luck to the squad.
He wrote on Instagram: "Today we start writing a new story. No matter the size and tradition of the opponents: we must respect and play each match with the focus of a final.
"It is important to play beautifully, yes, but it is also essential to leave everything on the pitch.
"Today, we will be more than 200 million hearts beating as one, vibrating with each achievement of our Selecao.
"I am sending all positive energies to you. I'm sure we'll have a happy ending. God bless you. Bring this trophy home!"
Brazil won Group G despite rounding off the pool stage with a shock 1-0 defeat to Cameroon after wins over Serbia and Switzerland. It faces Korea Republic in the last 16 on Tuesday (AEDT).