Bono: Dolly Parton didn't know she was so ill during final recording

U2's Bono has revealed Dolly Parton "did not know she was that ill" when she recorded her last-ever vocal.

The country music icon died at the age of 80 in August following a "brief battle" with cancer.

During an appearance on Jimmy Kimmel Live! on Thursday, U2 frontman Bono recalled how "mythical figure" Dolly seemed well when she recorded the track Torn for their new album Carnaval de Luz in Nashville, Tennessee in June.

"It was a masterclass. You forget her vocal range, and this was a woman, who sang on this song, honestly, she sang herself to some other place," he remembered. "We are told that she did not know she was that ill but it's her last prayer in a way, this song, it feels like a prayer. I think it's for America but anywhere where there is a divided politics."

Meanwhile, The Edge described how Dolly was fully committed to the duet.

"She was willing to put her musical destiny in our hands, 'cause we were doing something more sci-fi country. But she was so up for it, really game," the guitarist, real name David Evans, continued.

And Bono recounted how he pitched a more folk-like song, Life Long, to Dolly at one point. However, the Jolene hitmaker decided it was "too Irish" for her and instead suggested they collaborate on Torn. Johnny McDaid served as a co-writer.

"The implication (there was), of course, if I don't like where you take it, it will never see the light of day," he laughed.

U2's sixteenth studio album, Carnaval de Luz, was released on Friday.