Muhammad Ali pauses during training in Kinshasa, Zaire.
Photo by Abbas/Magnum

Muhammad Ali in ‘grave condition’ in Phoenix hospital

Updated
Muhammad Ali is in “grave condition” in a Phoenix-area hospital, a well-informed source tells NBC News, as the boxing legend continues to battle a respiratory condition.

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The 74-year-old former heavyweight champion was hospitalized on Thursday in Phoenix, Arizona, for what had initially been expected to be a “brief” stay, according to his spokesman Bob Gunnell.

A spokeswoman for his daughter, Laila, said, “Laila’s number one priority is her father’s well-being. She truly appreciates the outpouring of love for her family, as she spends quality time with her dad.”

Ali has been battling advanced Parkinson’s disease in recent years — an illness that experts say can lead to complications and affect the breathing of patients.

The boxing legend was previously hospitalized for several days in December 2014 and January 2015 after suffering a severe urinary tract infection initially thought to be pneumonia.

Although weakened by illness, Ali has continued to loom large on national stage.

RELATED: Muhammad Ali hospitalized in fair condition with respiratory issue

In recent months, Ali waded into the nation’s political fight after GOP presidential candidate Donald Trump suggested banning all Muslims from entering the U.S.

Ali, who famously joined the Nation of Islam in 1964, asked for more understanding.

“Speaking as someone who has never been accused of political correctness, I believe that our political leaders should use their position to bring understanding about the religion of Islam and clarify that these misguided murderers have perverted people’s views on what Islam really is,” Ali said in a statement.

But Ali has rarely been seen in public since last September, when he attended an awards ceremony by the University of Louisville honoring his prolific boxing career and legacy as a hometown hero. The Muhammad Ali Childhood Home Museum in Louisville opened earlier this month. 

This story originally appeared on NBCNews.com.

Muhammad Ali

Muhammad Ali in 'grave condition' in Phoenix hospital

Updated