The Give Me All Your Luvin robot has invited the pop superstar to join her on stage during her MDNA Tour, because "imitation is the highest form of flattery." That and Madonna probably wants to look like the ripped one now that GaGa has put on those few pounds she needed in the first place.

GaGa's writer-and-producer Vincent Herbert revealed: 'Madonna just called to ask Gaga to perform with her at Yankee Stadium. Her manager reached out to us and said Madonna would like Gaga to perform with her."

Seemingly, Madonna was so desperate to have GaGa, 26, join her that she even promised to give the money raised to charity. Unfortunately for the 54-year-old, Gaga's own work schedule meant she couldn't accept her offer. Shame.

Vincent is quoted by the Daily Mirror as saying: "She really wished she could do it. She said, 'If we do it, let's donate the money to charity.' But Gaga's committed to her own tour."

Madonna dedicated her song Masterpiece to GaGa recently, telling the crowd at a performance in Atlantic City: "I'm going to dedicate this next song to Lady GaGa. You wanna know something? I love her. I love her. I do love her. Imitation is the highest form of flattery. But one day, very soon, we're going to be on stage together. Just you wait. You think I'm kidding? I love Lady Gaga."

>Madonna has 'no comments' on Lady Gaga's 'obsession' with her
>Lady GaGa gets her own back at Madonna by flashing her bum.