Ed Sheeran has been working on his fourth album for six years.

Ed Sheeran

Ed Sheeran

The 'Castle on the Hill' hitmaker has revealed he already has a number of songs ready for his fourth album - which is expected to be called 'Subtract' - and teased it would be a "very acoustic record".

He said: "I've been working on this one since the same time as Plus. Every year I write a song that will go on it. So I have about six, seven at the moment.

"It's not necessarily experimental but I don't think there'll be any hot radio songs on it this time. It's a very acoustic record, very acoustic."

However, fans shouldn't get too excited as the 26-year-old singer admits it could be "three or four" more years before the LP is released.

He added: "It will potentially come later, because it's been about six years in the making and it might be another three or four. So I might put other stuff out before then, just to have something out. Next year I kind of want to do a couple of collaborations, some cool stuff."

And Ed is eyeing collaborations with the likes of DJ Khaled and Justin Bieber.

He told The Sun newspaper: "Me and DJ Khaled were talking about doing a song but I haven't had any time to go in the studio, so I missed this album. But hopefully next year. I'm keeping open.

"I'm always, always up for working with Bieber. He's doing a lot of these features (record collaborations) then he's touring. But when he wants to start making another album, I'd love to be involved. "I've got some ideas. I think he's really talented. And his head's screwed on properly now."