ABC spokeswoman Patrick Preblick said the lineup for the New Year's Eve special has not been announced.
The network "decided not to move forward" with booking Lambert on Kimmel's Dec. 17 show, ABC said in a statement.
Lambert addressed the two bookings on his Twitter account on Wednesday.
But all is not lost. NBC says he'll be a guest on "The Jay Leno Show" on Dec 21. And he's interviewed by Barbara Walters on her "Most Fascinating People of 2009" special -- airing next Wednesday on ABC.