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9:58 AM PT -- Our sources say doctors have informed Aretha's family today (Monday) is the day "Aretha will pass."

Aretha Franklin is gravely ill and friends and family are gathering for their final goodbye ... TMZ has confirmed.

A source very close to Aretha and a longtime dear friend tells TMZ he was told a week ago, "Prepare yourself, she's dying." The source adds Aretha was down to 86 pounds and her health was failing. The source says 2 weeks ago everyone in Aretha's circle was told "she could go any time."

Another source -- someone who has been close to Aretha for decades -- tells TMZ she has been battling cancer.

Franklin, who is 76, has been in poor health over the last few years. She has performed, but only on a limited basis ... most recently last November at an Elton John AIDS Foundation event.

The news that her health is failing first came from Roger Friedman over at Showbiz411, and WDIV TV in Detroit says Aretha's family confirmed she is gravely ill.