All I Want For X-Mas Is Miss...

Demi Lovato, Psy, Diana Ross for TNT Christmas special

Demi Lovato and Psy have signed up to headline this year's TNT Christmas special.

Diana Ross will also perform at the annual Christmas in Washington show on December 21.

Conan O'Brien will return to host the telecast, which will be recorded at Washington DC's National Building Museum for the second year running.

Smash star Megan Hilty, Voice finalist Chris Mann and American Idol winner Scotty McCreery will also perform.

Barack Obama and First Lady Michelle Obama will be among those attending the concert.

Justin Bieber, Cee Lo Green and Jennifer Hudson performed at last year's Christmas in Washington event.

TNT is broadcasting the show for the 14th time, while it has been an annual event for 31 years altogether.

What a welcomed return for Miss Ross - it has been a while since she last did a high profile TV apperance!