Obama will not attend Muhammad Ali memorial

Ali died last Friday at the age of 74 in hospital in Phoenix, Arizona, US.

World leaders will be among thousands attending Friday's procession and memorial service in Ali’s hometown of Louisville, Kentucky.

The White House said Obama and his wife Michelle will be at daughter Malia's high school graduation.

They will send a letter to the Ali family with White House senior adviser Valerie Jarrett, who knew Ali.

A spokesman for the Ali family, Bob Gunnell, said Obama and Ali's widow Lonnie had spoken by telephone.

Among those attending will be the president of Turkey, Recep Tayyip Erdogan, and King Abdullah of Jordan.

British former heavyweight champion Lennox Lewis and actor Will Smith, who once portrayed Ali on screen, will be among the pallbearers, according to the BBC.

The newspaper also reports that former US president Bill Clinton and actor Billy Crystal are also set to speak.

After Ali's death, Obama said he kept a pair of his gloves in his private study below the photograph of Ali beating Sonny Liston in 1964.

"Ali would be remembered not just as skilled a poet on the mic or as he was a fighter in the ring, but a man who fought for what was right. A man who fought for us," the US president said.

On Thursday, a traditional Muslim funeral service will be held at Freedom Hall, where Ali fought and won his first professional fight in 1960.

The funeral will be broadcast live on the internet.