US actor Don Cheadle is perhaps best known as Robert Downey Jr's sidekick in the "Iron Man" films. Now, he is using his celebrity muscle to make a movie about jazz icon Miles Davis.

But he needs more cash for the project – and has turned to crowdfunding website Indiegogo to make up the shortfall weeks before he makes his directorial debut shooting the relatively low-budget movie.

British blockbuster actor Ewan McGregor is also adding his star power to the long-gestating project, in which Cheadle will star as the "Kind of Blue" trumpet player.

"There are a lot of different mechanisms that go into us being able to get our budget, not least of which is me putting money in myself, which is supposed to be a cardinal sin in movie making," he told AFP.

"But I'm doing it because I believe in it and I want to do it," added the 49-year-old African American actor, who was nominated for an Oscar for 2004's "Hotel Rwanda."

Cheadle – who is due to return as "Iron Man" character Colonel James Rhodes in comic book blockbuster sequel "Avengers: Age of Ultron" next year – says he grew up with Davis' music.

He first had the idea of making a film about his musical hero in 2006 when Davis was inducted into the Rock and Roll Hall of Fame, but the project became a victim of the global financial crisis of 2008.

"We had several people bid on it. And then the world collapsed, the financial world, the carpet got pulled out from under everyone," he said, adding that it had been "very difficult" to resurrect it.

"We pulled it back and retooled it," he added of the film, which avoids a biopic-style overview, instead focusing on a period in the 1980s when Davis was trying to reboot his career after a so-called silent period.

Even so, the film has a budget of up to US$10 million (RM32.1 million). And Cheadle has turned to Indiegogo to help raise funds.

He is not the first star to use crowdfunding. Spike Lee, Zach Braff and Kristen Bell have used Kickstarter campaigns, with Bell netting a record US$5.7 million (RM18.3 million) for this year's "Veronica Mars," according to industry journal Variety.

Cheadle's campaign, launched June 3, raised a little more than half of its US$325,000 (RM1.04 million) target by this weekend. The funding drive is due to end on July 10. It can be seen at www.indiegogo.com/projects/join-miles-ahead-a-don-cheadle-film#home.

Filming is due to start in early July in Cincinnatti and last for six weeks.

"We're making it in two weeks' time and that money's gonna have to be there," Cheadle said in a June 23 interview. "It just has to so we're rolling the dice big and we're hoping people go check it out."

To entice people to pledge money, there are a range of "perks" for investors, ranging from CDs and T-shirts to set visits and lunch with Cheadle, and even an assistant producer credit on the finished movie for a US$25,000 (RM80,325) donation.

The actor – who has been learning the trumpet to prepare for the role – says Davis would have approved of crowdfunding, as he rejected the description of his music as jazz, preferring instead "social music."

"I take that inspiration and the way he lived his life, about the way we're trying to make this movie, doing outside the regular confines of moviemaking," said Cheadle, who recalls seeing Davis in the 1980s, before his 1991 death.

Now, Cheadle acknowledges that his own celebrity could help bring the musical icon to a wider public.

"It's my hope that we have created a story that isn't niche and isn't precious and doesn't require you to know anything about Miles Davis to come in and enjoy it," he said.

"Hopefully you come to the story and you learn the other things, and we smuggle in all the music that we can... But it's first and foremost a story about a man trying to figure out what to say."