Joaquin Phoenix has apologised to David Letterman for his infamous “horrible” appearance on The Late Show in 2009, just days before news that the long-running program has been axed.

The actor memorably appeared on former host’s Letterman’s talk show to promote the movie Two Lovers while in character for his mockumentary I’m Still Here.

As part of the mockumentary, Phoenix had publicly announced he was giving up acting to focus on a hip-hop career.

Appearing this week on The Late Show, now hosted by Stephen Colbert, the 50-year-old admitted he felt “stuck” because of his commitment to the project.

“It was strange, because in some ways it was a success and it was also just one of the worst nights of my life,” he said.

“As part of the promotion for a film that I had made, I was coming on the show, and so I was stuck.”

Noting he had begun adopting his hip-hop persona ahead of promoting Two Lovers, he said: “I had to keep it going.

“When I came on the show with Dave, I originally did the pre-interview in character, and I realised that it was just a little silly,” Phoenix said.

The Oscar-winning star said: “It was horrible, it was so uncomfortable, I regret it. I’ll never do it again. I’m so sorry.” 

Two days later, US television network CBS revealed The Late Show with Stephen Colbert will end in May 2026 after more than two decades on air.

“This is purely a financial decision against a challenging backdrop in late night. It is not related in any way to the show’s performance, content or other matters happening at Paramount,” CBS said.

CBS parent company Paramount is seeking approval from the US Federal Communications Commission for a $US8.4 billion ($A13 billion) merger with Skydance Media.

In July, Paramount agreed to settle a lawsuit filed by US President Donald Trump over an interview with former vice president Kamala Harris, his Democratic challenger in the 2024 presidential race, that CBS program 60 Minutes broadcast in October.

Colbert, a frequent on-air critic of Trump, told his audience on Thursday that he had been informed of the show’s cancellation the night before.

“It is a fantastic job … it’s a job that I’m looking forward to doing with this usual gang of idiots for another 10 months,” Colbert said on Thursday night local time.

Colbert was a regular on The Daily Show before he hosted The Colbert Report on Comedy Central. He took over The Late Show in 2015.

He thanked executives at CBS, his show’s audience and the 200 people who work on the show.

Senator Adam Schiff of California, a Democrat, was a guest during Thursday’s show.

“If Paramount and CBS ended The Late Show for political reasons, the public deserves to know. And deserves better,” Schiff wrote on social media platform X.

The Late Show first aired in 1993 with host Letterman.

– with AAP