Barrie-James O'Neill has dropped out folk rock band Kassidy to move to the United States with rumored fiancée Lana Del Rey.

O'Neill reportedly became engaged to the 27 year-old singer last year following a two-year romance, and now he has quit his band to relocate to America to pursue his solo career.

His exit sparked rumors Del Rey was behind the move, but O'Neill is obstinate it was a career-based decision.

In a message to fans, Scottish singer says, "I wanted to tell you that for whoever I disappointed and whoever I upset for my departure from the band Kassidy, I'm deeply sorry about that. I just had to go.

"My reasons were purely artistic. It was mainly a music thing. I had to be doing different stuff at this point in my life and those five years were the best five years of my life.

"I will never forget them and will never forget all of you great people who came to the shows when we were nothing and nobody knew who we were."

O'Neill now plans to step up his solo work as Nightmare Boy.