The 38-year-old rapper apparently never officially signed to perform at the event, reported Contactmusic.
A statement from his manager read, "Will.I.Am and his management received an invitation for Will.I.Am to perform at a New Year's Eve event on the beach in Rio de Janeiro, Brazil. During discussions about the invitation, the event producer expressed an intention to televise the concert."
"Will.I.Am's management team requested certain staging elements be added for the show in order to accommodate his televised performance. These staging elements were not confirmed, so no agreement to perform was ever reached," the note further read.
"(He) apologises to his fans for confusion caused as the result of the unauthorised and premature external discussion of his involvement," the statement said.