Adrian Belew has quit Nine Inch Nails.

The 63-year-old guitarist has parted ways with the band after a discussion with frontman Trent Reznor - who was inspired by Adrian to reform the group - in which the pair concluded his involvement was "not working" and he has apologized to fans for letting them down.

Adrian - who previously fronted band King Crimson and has worked with the likes of Frank Zappa, Talking Heads and David Bowie - wrote on his official Facebook page, "hey folks, before this goes too far let me say this: I greatly respect trent and the music he makes. no one is at fault. we both agreed it just was not working. I'm sorry to disappoint anyone. that really hurts. but NIN will do an amazing show and I am back where I belong: creating FLUX. (sic)"

His departure comes just a month after bassist Eric Avery quit, admitting he was "overwhelmed" at the thought of a long tour and instead wants to remain in Los Angeles to focus on his solo career.