Ed Sheeran says Pharrell Williams “forced” him to get out of his comfort zone.

The 23-year-old English singer-songwriter is preparing for the release of new album x, which features the track Sing, produced and co-written by the Happy hitmaker.

But Ed admits straying from his acoustic sound proved to be a challenge.

"Sing was a song that I did with Pharrell Williams and it was a very random studio session where he was forcing me to try new things and really pushing me outside my comfort zone and we just ended up with that song," Ed told Reuters.

"I think he knew how special it was and I needed a lot of convincing and I'm glad he convinced me.”

Ed hasn’t always worked with Grammy-winning producers like Pharrell, however.

The star scored his first major success with the release of his 2011 album +. But it wasn’t until he was featured on Taylor Swift’s hit single Everything Has Changed that he became a household name in the US.

He still credits the country music darling with propelling him to worldwide stardom.

"I think Taylor as a musician, as a person and as an entity is one of the biggest exports from the United States of America so to have her seal of approval, enough to take me on tour for six months was, you know, instrumental to me breaking the States,” Ed said.

"I'd been over to the States a lot. I'd had a bit of success there but just having that stamp of approval just took me from a theater artist to an arena artist and took me from a one hit to a household name."

x is now slated for a worldwide release next month.

Explaining his unusual choice of its title, the crooner said it’s his way of letting fans know there’s more to come.

“It’s a bit more of a well-rounded album. It’s more thought out, I think. Along the same trajectory as + but bigger, that’s why I called it x because it had made everything bigger,” Ed said.