"My prayers are with Aretha Franklin & her family during this hard time LOOK BELOW @ what I tweeted at the top of the year we MUST CELEBRATE the Living Legends while they are here to see it".
Gwendolyn Quinn, a spokesperson for Franklin, has also shared with ET that she was visited by Stevie Wonder on Tuesday morning.
"She is resting and surrounded by close friends and family", he wrote.
No further details have been revealed yet but the concert, which has been approved by Aretha, is likely to feature stars performing her best-known songs, including Say A Little Prayer, R.E.S.P.E.C.T and (You Make Me Feel Like) A Natural Woman.
The 76-year-old music icon is believed to be "gravely" ill, and whilst her family are said to have gathered round to say their goodbyes, they're thankful for the "outpouring" of support they and the Queen of Soul have received since the news was first reported.
Aretha Franklin is in good hands.
India’s three-time prime minister Vajpayee dies at 93
All government offices, schools and colleges to remain shut across the state. My condolences to his family & all his admirers.
"Family is there with her".
Beyoncé and Jay-Z paused their Detroit concert on Monday after the show's opening song "Holy Grail" to pay a small tribute to Franklin. "This is it", she told WDIV in February 2017, adding that she would still take the stage at "some select things".
"We visited and prayed with @ArethaFranklin today", Jackson later tweeted, "Please continue to keep her in your prayers".
After turning 18, Franklin confided to her father that she aspired to follow Sam Cooke to record pop music.
Fans, friends and musicians influenced by Franklin offered positive words to the iconic singer when news broke that she was ill, including Rod Stewart, Mariah Carey, Chaka Khan, Lin-Manuel Miranda, Tyler Perry, Missy Elliott and Wayne Brady.
"We love you", Beyoncé said, adding a word of thanks for "the handsome music".
Aretha - whose three siblings all died of cancer - has battled ill health over the last few years and in 2011, denied she was suffering from pancreatic cancer, though she later admitted she'd had a tumour removed. "She's definitely a queen and she's incredible so I really feel for her".