Actor Robert De Niro has revealed that his artist father was gay in a new HBO documentary called, "Remembering the Artist: Robert De Niro, Sr.," and in a new interview with OUT magazine.

De Niro, who took it upon himself to preserve his abstract expressionist painter father's Soho, New York, studio, directed the documentary about his late father, who died of cancer in 1993.

The actor reads his father's personal journals in the film and reveals the elder De Niro's conflicts over coming to terms with his homosexuality.

"He probably was (conflicted about his sexuality), being from that generation, especially from a small town upstate (in New York)," De Niro tells OUT magazine in an interview about the production.

"To me, he was always a great artist. Yeah, he probably was [conflicted about being gay], being from that generation, especially from a small town upstate (Syracuse, New York). I was not aware, much, of it. I wish we had spoken about it much more. My mother didn't want to talk about things in general, and you're not interested when you're a certain age.

"For my kids, I want them to stop and take a moment and realise that you sometimes have to do things now instead of later," he adds, "because later may be 20 years from now - and that's too late."

"Remembering the Artist: Robert De Niro, Sr." was screened at the Sundance Film Festival back in January, and the actor says that making the film was a labor of love.

"I felt I had to. I felt obligated," De Niro says. "It was my responsibility to make a documentary about him... It was not intended to be on HBO. It was just something I wanted to do."

The actor also shared that he and his dad were somewhat close, but they didn't spend much time together.

"We were not the type of father and son who played baseball together, as you can surmise," he explains. "But we had a connection.

"I wasn't with him a lot, because my mother and he were separated and divorced... He was absent in some ways." (De Niro's parents split shortly after he was born in 1943). [But] he was very loving. He adored me... as I do my kids."