Celine Dion almost missed out on the biggest hit of her career to date after initially passing on Titanic theme song My Heart Will Go On.

The power ballad has become the French-Canadian superstar's signature tune, but she really wasn't a fan of the track the first time she heard it, and was so reluctant to lay down the vocals in the studio, the final cut was made with the demo her late husband and manager, Rene Angelil, convinced her to record.

"You know what? This one song that I didn't want to record - and I'm glad that they (management team) didn't listen to me - (was) My Heart Will Go On. It is true," she confessed during an interview on America's Watch What Happens Live on Monday night (18Nov19).

Explaining why she was hesitant to jump onboard the 1997 project, Celine shared, "It didn't appeal to me. I was probably very tired that day... and my husband said, 'Let's hold on...'

"He said, 'Let's try to make a little demo,' and I sang the song once, and they built the orchestra around it. I never resang it for the recording, so the demo is the actual recording, but after that, I've sang it about three gazillion times (sic)!"

Celine wasn't the only one who couldn't envision the hitmaking potential of My Heart Will Go On - musician David Foster reveals he turned down a request from the singer to produce the single.

"I said, 'I don't like the song, I don't wanna do it,' so I was right there with her! And then I passed on it," he told U.S. breakfast show Today on Tuesday. "I don't know why, it just didn't (have that thing) for me. I couldn't have made a bigger mistake!"

Walter Afanasieff, composer James Horner, and Simon Franglen ended up producing My Heart Will Go On, which sold more than 18 million units worldwide, becoming one of the biggest-selling songs in pop history.