Muhammad Ali is still in hospital two days after being admitted with a respiratory issue.
There has been no official update on Ali's condition but an enormous number of goodwill messages have been posted on social media by boxers and fans.
The 74-year-old, was diagnosed with Parkinson's Disease in 1984.
The three-time former world heavyweight champion was admitted to hospital in December 2014 with a severe urinary tract infection.
Concern about Ali's current condition has grown throughout Friday.
Great Britain's newest world champion Tony Bellew has been among those expressing hope for his recovery.
One of the most high-profile global sporting stars, Ali's name transcends sport like few others.