Michael Buble praised his children for giving him "perspective" and said that he was unaware how much he would enjoy being a father just weeks before confirming his son Noah, three, has been diagnosed with cancer.
In Buble At The BBC, which aired on Thursday night, the singer told host Claudia Winkleman he "just didn't know that level of love existed".
He said of his sons: "I just love them so much that part of loving them so much is not giving them everything they want and that is a tough thing for me."
When asked about returning to work, he said it was "really tough", and that Noah did not want him to leave.
He said: "My son Noah is three, Eli is eight months, and Noah said to me 'Poppy, for what are you going?' I said 'Well, daddy is going to go and sing'.
"And it kills you, he said 'Please don't go, I will be a good boy', and I think I'm the worst human being in the universe."
During a recent appearance on ITV's Loose Women, the 41-year-old said: "The only regret that I have in my life is that I took this long to have kids, because I had no idea the perspective it would give me.
"I had no idea how much I would love being a dad. That's it, that's all I care about ... I love them too much probably, if there was such a thing.
"It's made everything else so insignificant, moments that I was afraid of and moments that would overwhelm me have now become a joy because I've realised how not serious they are compared to what is really important, which is Noah and Eli and that's it."
Michael and wife Luisa Lopilato married in 2011, before welcoming Noah in August 2013.
They are also parents to nine-month-old son Elias.
Michael was recently announced as the host of the annual Brit Awards ceremony in February 2017.
According to reports, Noah was diagnosed after he and his mother travelled to the US due to health concerns.
The type of cancer he has has not been revealed.