Tom Hiddleston has defended his portrayal of country music legend Hank Williams in a new biopic, insisting he understands the "huge responsibility" to fans and has been practising his music skills every day.

The Thor actor will play the tragic star in I Saw The Light, a new film which will chronicle Williams' meteoric rise to fame and his untimely death at the age of 29 in 1953.

However, the casting of a Brit in the role has sparked debate among fans, and drawn criticism from late star's grandson, Hank Williams Iii, who insisted an American actor should have been picked by casting bosses.

Hiddleston has now spoken out to assure fans he will do everything he can to make sure Williams' story is accurately portrayed.

He tells Britain's Daily Mail newspaper, "The film is about the man behind the myth, the power of his music, the sheer voltage of his talent and charisma, and his formidable demons... Hank's life has a tragic arc, but in simple truth, he was a genius: a star that burned twice as bright and lived half as long. It's a huge role for me and a huge responsibility. I'm going to give it everything I've got."

The actor also insists he is working hard to improve his musicianship and has been practising with Grammy Award-winning country star Rodney Crowell.

He adds, "I've already started singing and playing every day... He (Crowell) came down to visit me over the Easter weekend in Toronto where I was filming... and we jammed for a day or so. It was so exciting... It was spine-tingling just to spend a day playing some of Hank's greatest hits... with such a gifted musician. He's already expanded my vocal range and given me a few pointers about adapting my own tone to sound like Hank. Rodney has furnished me with his beautiful J45 Gibson (guitar) to practice with. And he'll be on hand throughout the shoot."