Jason Mraz reckons 'I'm Yours' was such a big hit because it is "like a nursery rhyme".

The singer acknowledges the infectious quality of his international breakthrough single, saying it stems from the song's simplicity.

He said: "It's a blessing. Damn straight. When I first wrote it, I thought it was a nursery rhyme or something in that genre.

"As time went by, I realised we never really forget our nursery rhymes and I realised it had that staying power, there's something simple about it."

"I'm surprised at how simple it is. There's not a whole lot going on, it's muted guitar, vocal and drum beat."

The singer is now undergoing to task of writing follow up songs to his massive hit for his fourth album, which is slowly coming together.

He added to website Hitfix.com: "At the moment, it's still a great big block of cement and we're just starting to chip away at it to see what the sculpture's going to look like.

"I've got big stack of songs. Now it's on to the process of recording and listening and seeing what the album in that is."