An Andy Warhol self-portrait completed shortly before his death is expected to sell for as much as $40 million at auction next month, Christie's said on Wednesday.

"Self-Portrait," a large haunting depiction of Warhol rendered in deep red and black, was done in 1986 and displayed in a widely praised gallery show in London just months before he died after routine surgery in New York.

"It is a rare event that a work of this grandeur and stature comes to market," said Amy Cappellazzo, Christie's international co-head and deputy chairman of post-war and contemporary art.

"With all the other examples in museums, it will be the last chance that buyers will have to bid on a work that shifted art history," she added about the sale on May 11.