AceShowbiz - Wrestler-turned-actor Dwayne Johnson was forced to abandon an attempt at serenading a fan with breast cancer after struggling to keep his voice from cracking during the opening lines.

The "Jumanji: The Next Level" star tried to croon Garth Brooks track "Much Too Young" for a woman named Melissa, who has been battling Stage 4 cancer for the last six years, but he barely made it through the first few lyrics.

In a video shared to Instagram, he began, "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."

Johnson then added, "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."

However, after his voice kept cracking, the action man had to quit, "I'm so sorry, I sing in keys that don't exist."

"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 (sic)."

Despite his botched musical tribute, Johnson hoped his video would bring happiness to his fan, "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 (sic)!" he quipped in the accompanying caption.

Although Johnson couldn't hit the same high notes as Brooks, he previously proved his musical talents in Disney movie "Moana", in which he voiced the character of Maui and sang the tune "You're Welcome".