Muhammad Ali, 74, Hospitalized for Respiratory Issue

The 74-year-old boxing legend is being treated for a respiratory issue, his rep tells ET in a statement, adding that the Ali family "respectfully requests privacy" during this time.

"Ali, who suffers f-rom Parkinson's disease, is being treated by his team of doctors and is in fair condition. A brief hospital stay is expected," the statement reads.

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The Olympic gold medal-winning boxer was diagnosed with Parkinson's disease in 1984.

He was hospitalized twice in one month in late 2014-early 2015 for what was thought to be a mild case of pneumonia but was later determined to be a "severe" urinary-tract infection, according to the Associated Press.

A source close to Ali tells ET that he has been battling this respiratory issue for "some time." "He was invited to the Prince tribute held in Los Angeles a couple weeks back but could not make it because of this very issue," we're told.

Meanwhile, another source reveals that Ali is "getting weaker" and it is "harder for him to recover f-rom chronic health issues."

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ET previously spoke with two of Ali's daughters, Maryum and Hana, who opened up about their father's state of health.

"I call my father in the mornings and that's when he's at his best," Hana said. "His voice is clearer, speaks slow but you can hear him. He has family around him and he's enjoying life."

Listen to more of their intimate details about their dad in the video below.