Muhammad Ali's doctor says the iconic boxer had been "having a tough time in the last year" before his death.

The three-time world heavyweight champion, who had Parkinson's disease for 32 years, died aged 74 from "septic shock due to unspecified natural causes" according to his family.

"The last week has been particularly tough," said Abraham Lieberman, who was with Ali only hours before he died.

"It became apparent God wanted him and we all became reconciled to it."

Lieberman told BBC Radio 5 live's Sportsweek: "Everyone in the back of their minds expected something bad was going to happen but you always hope you will beat the odds because he is someone who always beat the odds - he is not an ordinary person.

"He stood up for his beliefs and what he thought was right. He treated everybody from the humblest person to the biggest celebrity the same - which was fair.

"You could not believe how nice he was outside the ring compared to the way he was inside the ring. I lost a great friend."

Lieberman, a director of the Muhammad Ali Parkinson Center in Arizona, rejected suggestions that boxing was solely responsible for Ali's illness.

"I don't think it helped but I think he developed it slowly over a number of years," he said.

"People that develop Dementia Pugilistica are usually dead within three or four years - he's had Parkinson's for over 30 years.

"It started on one side, his brain looked relatively good on MRI scan, I can't tell you boxing didn't have a role but I think he had regular Parkinson's disease."

The doctor recalled a story from many years ago when Ali visited an elderly man in a nursing home, who mistook him for another great boxer, Joe Louis.

"Muhammad said: 'If it gave that old man pleasure to think he met Joe Louis - then I'm Louis.'," he said.

"I think that summed up Muhammad, he was a great personality but really a kind person, with tremendous feeling of sympathy for people."

Lieberman said Ali had been supported by his family throughout his illness.

"His Parkinson's got worse but he had a very devoted family who really treasured him and gave him as much quality of life as you could have," he said.

Former boxer Joe Bugner, who fought Ali twice, was also a guest on Sportsweek and the 66-year-old, speaking from his home in Australia, said: "He and I became one of the closest friends in the boxing world.

"He was unique, not only was a great, great boxer and athlete but also very intelligent and nobody could outwit him as far as the words were concerned."