A performance featuring Adam Lambert and British rock group Queen at Sonisphere 2012 has been canceled, the BBC reported.

“It is with very heavy hearts and much regret that we announce the cancellation of Sonisphere Knebworth 2012,” Queen announced on its official website on Wednesday.

An official statement from festival organizers is expected on Thursday.

After much speculation in the media, Lambert confirmed the date in February. “As many suspected, I can finally confirm: I have been invited by Queen to sing one very special concert! Sonisphere at Knebworth July 17th!” Lambert tweeted to his more than 1.3 million followers. “Sorry to be coy about the details the past few weeks, but I made a promise to keep it under wraps as best I could. Gonna be a surreal night!”

Lambert has denied rumors that he would join the iconic rock band, which currently includes guitarist Brian May and drummer Roger Taylor. Taylor and May formed the band Smile, which Freddie Mercury altered to Queen when he joined. Mercury died in 1991 of complications due to AIDS.

Lambert and Queen are still scheduled to perform together on June 30th at Moscow's Olympic Arena. ?