A rep for Adam Lambert has neither confirmed nor denied that fun. will perform with the singer and Queen tonight (September 20) in Las Vegas.

The British rock band and the 'Trespassing' star are due to play at the iHeart Radio Music Festival and it had been mooted that some special guests might appear.

Industry bible Billboard reported that 'We Are Young' stars fun. would join Queen + Adam Lambert on stage to possibly play the tracks 'Somebody to Love' and 'Fat Bottomed Girls'.

Pressparty reached out to Lambert's rep regarding the rumours, but they neither confirmed nor denied the speculation.

With only hours to go until the performance, excitement is reaching fever pitch within fans of the 'Better Than I Know Myself' star.

Other names meanwhile due to perform tonight at the MGM Grand include Katy Perry and Robin Thicke.