Madonna and Britney - Touring Together

To return the favor, Madonna will most likely make an appearance during Britney Spears' "Circus" tour.

Britney recorded a video clip played during Madonna’s "Sticky & Sweet Tour", and appeared on stage in person at her Los Angeles gig last month.

The only obstacle at the moment is timing, according to Wade Robson (Britney's choreographer).

“There has been talk of Madonna making an appearance and there’s so many places we could take that”. “At this point the main issue is timing.”