The hip-hop star was due to perform at the Bonnaroo festival in Manchester, Tennessee, but he has now confirmed he is too ill to go ahead with the show.
In a post on his Twitter.com page, he writes, "To everyone at Bonnaroo: I'm sorry I can't make it. I'm really really f**king sick but I will make it up to Tennessee as soon as I possibly can."
He goes on to confirm he is battling a bout of potentially-deadly lung infection pneumonia, adding, "To everyone who think (sic) I'm being overdramatic, go get pneumonia and then try singing (my song) Whoa all the way through... I'm just sayin (sic)."
The news is a further blow to festival organisers following the cancellation by Mumford & Sons. The band has axed a number of dates in the U.S. after bassist Ted Dwane was hospitalised to undergo brain surgery.