Pop icon Madonna may have fired another salvo in the ongoing musical feud between her and Mother Monster Lady Gaga.

The Material Girl reportedly may be using her upcoming concert tour as a forum to perform a Material Girl/Mother Monster mash-up.

During a recent concert rehearsal in Israel,  Madonna was caught on video performing her 1989 composition, "Express Yourself," before transitioning into Lady Gaga's "Born This Way," complete with the sound of a revving motorcycle that is Gaga's trademark.

Madonna seamlessly flipped back and forth between the choruses of both songs to further illustrate the similarities.  She ended with a drum-driven remix of "Express Yourself" and chanted chorus of "Respect yourself … she's not me."

Whether it was an homage or a pointed dig went unstated, but Madonna told "Nightline" anchor Cynthia McFadden in a January interview that  Lady Gaga's hit song "Born This Way"  felt "reductive" of "Express Yourself."

Watch: Lady Gaga talks about faith and family, and sings "Marry the Night."

Lady Gaga has made her mark with a unique style of dress and music that many say is reminiscent of  Madonna's iconic style and attitude.

And it's no secret that the "Poker Face" singer admires Madonna; she has spoken of her regard for the pop icon. But  the admiration apparently is not mutual.

Last year when a Belgian magazine's reporter asked Madonna about her fans, including Lady Gaga, the singer replied, according to the magazine:  "I have no comment on her obsessions related to me, because I do not know if it is based on something profound or superficial."