Mahershala Ali poses with the award for best performance by an actor in a supporting role for "Green Book" in the press room at the Oscars on Sunday, Feb. 24, 2019, at the Dolby Theatre in Los Angeles. Picture: AP
Mahershala Ali says it's "frustrating" that black actors have to fight to get leading roles.

The Oscar-winning actor's major career breakthrough came playing fixer Remy Danton in 'House of Cards' and he thinks the role gave other casting directors "permission" to put him in their projects.

He said: "I had many years of auditioning, booking gigs, almost booking jobs and making some real allies in the business - people who wanted to cast me in things but I just wasn't a big enough name.

"What 'House of Cards' did was give people permission to cast me.

"It can be frustrating. Just to be frank with you, African-Americans don't really get cast on potential.

"I hope that now I will have a window where I can finally do a lot of the kind of work I've been wanting to do for a long time.

"I've spent a long time playing the man next to the man next to the man. Finally, I'm getting to play the man!"

The 45-year-old star plays Wayne Hays in 'True Detective', a role originally written for a white actor, but Mahershala persuaded series creator Nic Pizzolato it would work better if the cop was black.

He told heat: "I found myself really responding to Wayne and his journey.

"It was the only character I was really interested in playing. I felt like it would be more interesting in terms of the narrative to see a black lead detective in 1980 navigating a homogenous community in the South while trying to solve this crime.

"Hayes already stands out, just as a lay person. But now he's a police officer trying to operate wihin this community...

"I even sent some pictures of my grandfather (a former cop) to Nic, as a way of pushing home the point of how the drama would be heightened if the character was black."