Madonna is to sell a Fernand Léger Cubist painting to help raise money for girls' education projects in countries including Afghanistan and Pakistan, the auction house Sotheby's has announced.

The singer, a keen collector who owns works by Frida Kahlo and Tamara de Lempicka, bought Léger's Trois Femmes à la Table Rouge in 1990. It will be sold in New York on 7 May with an estimate of $5m-$7m (£3.3m-£4.6m) and all proceeds are to benefit the Ray of Light Foundation.

Madonna said she wanted to "trade something valuable for something invaluable". She said: "I have a great passion for art and a great passion for education. In conjunction with Sotheby's, I would like to share these two passions.

"I have chosen to auction this painting called Three Women by Fernand Léger and donate all the proceeds to support girls' educational projects in Afghanistan, Pakistan and other countries where female education is rare or nonexistent.

"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."

The work, painted in 1921, is part of Léger's Mechanical Elements series, examples of which are in institutions such as the Dallas Museum of Art and the Beyeler Foundation in Switzerland.

It will be shown at Sotheby's headquarters in London between 12-16 April before heading back to New York for the sale.