Earlier this month, Adam Lambert said he wasn't confirming any appearances with Queen this summer. The operative term was "confirming."

Because today, the "American Idol" star is now definitely confirming he'll be fronting the classic rock band -- with original band members Brian May and Roger Taylor -- during their headlining performance at the Sonisphere Festival in England on July 7.

"As many suspected, I can finally confirm: I have been invited by Queen to sing one very special concert!" he Tweeted. "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!"

Queen joins headliners like Kiss and Faith No More at Sonisphere U.K., held in Knebworth Park; Queen's original frontman Freddie Mercury’s last performance with Queen was also at the same park-venue in 1986.  Tickets for Sonisphere go on sale on Thursday (Feb. 23).

Lambert performed "We Are The Champions" with May and Taylor on the FOX reality show 2009. They reunited at the MTV EMAs in Belfast in November.

Lambert's next album "Trespassing" has been bumped from March 19 to later in the spring.