Dwayne The Rock Johnson's voice cracks during serenade for fan with breast cancer

Dwayne Johnson filmed a sweet serenade for a fan who has breast cancer, but it did not go to plan. Photo / Getty Images

Dwayne 'The Rock' Johnson attempted to serenade a fan with breast cancer - but his voice cracked after the first line.

The 49-year-old actor was "so excited" to send a personal musical message to a woman named Melissa, who has been battling Stage 4 cancer for the last six years, but he struggled to get to grips with the higher notes in his chosen song, Garth Brooks' Much Too Young, and had to terminate his performance.

He said in a video shared to Instagram: "I'm so excited right now to deliver this very special message. I'm so excited my cheeks are red. This goes out to a very special woman. A very strong woman. Melissa, A.K.A Missy!"

"I want to say first of all, thanks for being a fan, I am honoured and I know you are fighting hard, and I know that you're home. Keep fighting and keep staying strong Missy.

"I also know you're Garth Brooks' biggest fan... You know I love my country music. So in the spirit of Garth, this one's for you."

But after his voice kept cracking, the former wrestler ultimately gave up his attempts to sing after just two lines.

He added: "I'm so sorry, I sing in keys that don't exist.

View this post on Instagram

A post shared by therock (@therock)

"I'm gonna let Garth sing, he'd be honoured to know you're a fan of his Thank you and keep staying strong and inspiring all those around you, including us. We love you Missy, stay strong."

Despite his botched musical tribute, the Moana star hoped his video would bring happiness to his fan.

He captioned his post: "I apologize about my singing in keys that don't exist and sounding like I'm experiencing puberty again. I hope this makes you smile, Missy!"

Johnson's sweet video came just a month after he recorded himself singing his Moana alter ego Maui's song You're Welcome for a 4-year-old cancer patient named Indy Llew Jones.

He wrote at the time: "Stay strong honey and keep singing your songs."