Several artists have already dropped out of the festival, which is being held to celebrate the 250th anniversary of the United States' Declaration of Independence. Among them are Martina McBride, Young MC, Morris Day and the Commodores.
Fab Morvan of Milli Vanilli says in an interview with CNN that this is not "what I agreed to," and that he was told the festival would not be politically connected.
"I was there to unite the people," he says, adding that it has since turned into a circus.
According to Variety, Vanilla Ice is the only one who is still openly interested in participating. Flo Rida has not commented.
The festival is being held in Washington between June 25 and July 10.
