The singer dedicated her track "Masterpiece" to the younger star during a performance in Atlantic City, New Jersey, over the weekend, and appeared to accuse her of imitating her, reports contactmusic.com.
Madonna told the crowd, "I love her. I love her. I do love her. Imitation is the highest form of flattery." She then cryptically added: "And one day, very soon, we're gonna be on stage together. Just you wait."
Madonna, 54, has previously accused Gaga, 26, of copying her track "Express Yourself" on her single 'Born This Way'. "I thought, 'What a wonderful way to redo my song'. I mean, I recognised the chord changes. I thought it was... interesting," said Madonna.