Image caption George Lucas has invested $93m (£60m) of his own money into the movie

Director George Lucas says it took 20 years to get his latest film made, "because it's an all-black movie".

Speaking on The Daily Show, Lucas said he had to self-fund Red Tails, the true story of a group of African-American pilots who fought in World War II.

He claimed major film studios would not back the movie because "there's no major white roles in it at all".

"I showed it to all of them and they said, 'No. We don't know how to market a movie like this,'" he said.

"They don't believe there's any foreign market for it, and that's 60% of their profit," he added.

Lucas co-wrote and produced Red Tails, which which was directed by Anthony Hemingway.

It features several well-known names - including Oscar-winner Cuba Gooding Jr, Terence Howard and R&B star Ne-Yo - and shows how the pilots were segregated and kept on the ground for most of the war, until they were called up to fight for their country.

The real-life airmen featured in the drama were given a Congressional Gold Medal by then-President George Bush in 2007.

'Invisible' audience

Lucas put $58 million (37.8 million) of his own money into the movie. It will be released by his company Lucasfilm, and distributed by Twentieth Century Fox.

He is putting a further $35 million (£22.8 million) towards the distribution costs, said trade paper The Hollywood Reporter.

"It's a reasonably expensive movie," Lucas told Jon Stewart on The Daily Show. "Normally black movies, say Tyler Perry movies or something, they're very low budget.

"Even then, the [Hollywood studios] won't really release his movies, it goes to one of the lower, not major distributors.

"This [film] costs more than what those movies make," Lucas added.

Director and actor Perry, whose movies include Why Did I Get Married and the Madea series, is one of the most profitable film-makers in the US.

However, he retains the rights to all his work - which plays almost exclusively to black audiences - and has previously stated that his fans are "invisible" to the Hollywood mainstream.

Lucas's comments echo those of Spike Lee, who criticised the lack of black faces in Hollywood war movies in 2008.

Speaking about Clint Eastwood's movies Flags Of Our Fathers and Letters From Iwo Jima, Lee said: "He did two films about Iwo Jima back to back and there was not one black soldier in both of those films".

"I know it was pointed out to him and that he could have changed it. It's not like he didn't know."

Eastwood later justified his choice of actors on Flags Of Our Fathers, saying that the African-American troops who did take part in the battle of Iwo Jima were not involved in the key incident in the film - where US marines raised the American flag on Mount Suribachi.

The veteran actor argued that if he had deliberately "put an African-American actor in there, people would go: 'This guy's lost his mind'".

Lucas insisted that Red Tails was nothing like preceding war films, including 1989's Glory which, although it starred Denzel Washington, featured "a lot of white officers running these guys into cannon fire".

If his film does well at the box office, Lucas said he had a prequel and sequel planned.