The world begins two final days of mourning for Muhammad Ali on Thursday when the boxing great will be honored with a Muslim funeral a day before receiving a final goodbye with an interfaith service.

Ali, one of the transcendent figures of the 20th Century for his boxing prowess, showmanship and opposition to the Vietnam War in the turbulent 1960s and '70s, died last Friday of septic shock in an Arizona hospital. He was 74.

Some 15,000 people are expected at the jenazah, the Arabic word for funeral, set for noon (1600 GMT) at Freedom Hall in Ali's home town of Louisville, Kentucky, the venue where Ali defeated Willi Besmanoff on 29 November 1961.

Imam Zaid Shakir, co-founder of Zaytuna College in Berkeley, California, will lead the service.

Ali and his family planned his funeral for 10 years, making sure it would honor his Muslim faith.

Ali's braggadocio startled white America even when he went by his birth name, Cassius Clay. He further shocked US society after he joined the Nation of Islam and changed his name in 1964.

In the 1970s, Ali converted to Sunni Islam, the largest denomination among Muslims worldwide. Late in life he embraced Sufism, a mystical school of the faith.

He was admired worldwide, and gave US Muslims a hero they could share with the American mainstream.

"To be properly prepared for burial, prayed over and then buried is a right owed to every single Muslim," Shakir said in a statement issued by the Ali family spokesman. "If no one fulfills those rights, then the entire community has fallen into sin. In the case of someone of Muhammad Ali's stature, to leave any of those rights unfulfilled would be a crime."

On Friday, the final service at the KFC Yum! Center will take place with luminaries such as former US president Bill Clinton, Turkish president Tayyip Erdogan and comedian Billy Crystal.

Actor Will Smith, who portrayed Ali in a 2001 biographical film, and former heavyweight champion Lennox Lewis will be among the pallbearers.

On Wednesday, the city of Louisville held a celebration called the "I Am Ali" Festival. The day-long event highlighted Ali's life through stories, music, dance and arts and crafts that had children coloring butterfly and bee masks in an homage to the boxer's famous quote about his fighting style, "Float like a butterfly, sting like a bee."