Pop singer Madonna will auction off a 1921 cubist painting from her own art collection to raise funds for charity.

Her painting by French artist Fernand Leger, titled "Trois Femmes a la Table Rouge," will be offered at Sotheby's in New York on May 7th with an estimate up to $7 million.

Madonna says the sale proceeds will go to her Ray of Light Foundation and its education projects in Afghanistan and Pakistan.

She said in a statement, "I cannot accept a world where women or girls are wounded, shot or killed for either going to school or teaching in girls' schools. We don't have time to be complacent. I want to trade something valuable for something invaluable - educating girls! Knowledge is power. Let's change the world!"

Madonna bought the work in 1990. It will take a tour to Hong Kong and London before returning for display in Sotheby's New York galleries ahead of the sale.