Muhammad Ali's funeral is to be held in his hometown of Louisville at 2pm local time on Friday.
The service, at the KFC YUM! Centre in the Kentucky city, will be open to the public and streamed live on the internet for those unable to attend.
It will be preceded by a Jenazah - an Islamic funeral prayer programme - also for the public at midday on Thursday at the Freedom Hall, where Ali made his professional debut with victory over Tunney Hunsaker in 1960 and fought for the last time in Louisville against Willi Besmanoff a year later.
Among the talkers at "The Greatest's" funeral will be Malcolm X's daughter Attalah Shabazz, wife Lonnie Ali, eldest daughter Maryum, American actor Billy Crystal, former US president Bill Clinton and Recep Tayyip Erdogan, the president of Turkey.
"Everything that we're doing here was blessed by Muhammad Ali, and was requested," said family spokesman Bob Gunnell, who broke the news of the former world heavyweight champion's death at the age of 74 on Friday.
"He wanted the memorial service to reflect his life, and how he lived. He wanted everyone to be able to attend. He was the people's champ, and he wanted the memorial service to reflect that.
"We want this to be inclusive of everyone. That's why we set Freedom Hall - not just with its historical significance - but with the size of Freedom Hall, so that everyone fits in.
"That Muslims and people of all faiths could attend, and perhaps learn more and be like Muhammad Ali, and open their hearts to everybody.
"(We expect) 15,000 people at the Yum! Centre, and 18,000 at Freedom Hall.
"This is not a political statement, this is not about politics, this is about how Muhammad Ali lived his life."
Ali, formerly named Cassius Clay, died in Phoenix, Arizona, at the age of 74 on Friday evening local time. He had been admitted to hospital earlier in the week with a respiratory condition having suffered with Parkinson's disease for 32 years. His family said in a statement that he died from complications related to his condition.
Since then, tributes have been as widespread as they have been heartfelt, with one-time rival George Foreman and long-term friend and business manager Gene Kilroy among those to tell Press Association Sport of their sense of loss.
"Each time one of us leaves, I tell everybody: Muhammad Ali, Joe Frazier, George Foreman, we were really just one guy," Foreman said. "And every time one slips away, you feel like you've lost a piece, and Muhammad Ali was the greatest piece of all."