The 'Michael Forever Tribute' event will take place at Cardiff's Millennium Stadium in Wales on October 8, and will feature performances from the likes of Leona Lewis, Christina Aguilera and JLS.
Michael's brothers Jermaine and Randy have criticised the concert for its timing, as it coincides with the manslaughter trial of the late singer's doctor Conrad Murray.
The singer confirmed to CNN that she would find it "too difficult" to appear at the tribute due to the inappropriate timing.
"Because of the trial, the timing of this tribute to our brother would be too difficult for me," her representative said.
The gig will be broadcast around the world in both 2D and 3D and will be attended by Michael's family members and friends. Tickets for 'Michael Forever' are on sale now with prices starting at £55.
Janet Jackson performed a tribute to her late brother by singing their duet 'Scream' during her London tour in July.
Watch the video for Michael and Janet Jackson's 'Scream' below: