Ben Heppner, seen performing as Siegfried in Gotterdmmerung in Aix-en-Provence, France in 2009, has withdrawn from the Metropolitan Opera's Ring Cycle.' ((Anne-Christine Poujoulat/AFP/Getty Images))

Canadian tenor Ben Heppner has withdrawn from the Metropolitan Opera's ambitious new staging of Wagner's Ring Cycle by acclaimed director Robert Lepage.

The B.C.-born Heppner, 55, is bowing out because he "has retired the role from his repertory," the celebrated Manhattan opera company said in a statement Tuesday.

In 2007, the Met announced the casting of Heppner as Siegfried with great fanfare.

The role, which he was to perform in the final two operas of the cycle (Siegfried and Gotterdammerung) during the 2011-12 season, is considered one of the most challenging and difficult tenor parts in all opera.

The casting would have been the first time Heppner had performed Siegfried at the Met. He previously performed the role at festivals in Aix-en-Provence, France and Salzburg, Austria.

Heppner was unavailable for comment on Tuesday evening. But his manager, William Guerri, told the New York Times that the singer found the role "difficult" and not "gratifying."

"He’s the most famous Wagner tenor of our time," Guerri said. "But all Wagner roles weren’t written for one voice."

Tenors Gary Lehman and Stephen Gould will replace Heppner in the operas, the Met said. The cast also includes Deborah Voigt, Bryn Terfel and Jonas Kaufmann.

Though considered among the world's top performers of Richard Wagner's operas, Heppner has on occasion suffered vocal troubles that have affected him during performances or forced him to postpone or cancel engagements.

A nagging illness also forced him to cancel a recital appearance in Toronto for the Canadian Opera Company's 60th anniversary in 2009.

Quebec stage wizard Lepage debuted his first Ring Cycle instalment — a costly, awe-inspiring and high-tech Das Rheingold — at the Met in September 2010.

With files from The Associated Press