The song will raise money for a charity set up by The Edge (left)

The bands - two of the world's most popular rock groups - will record a version of The Skids' The Saints Are Coming, a minor hit from 1978.

Green Day's website said U2 asked them to appear on the song to raise money for The Edge's charity Music Rising.

The fund helps replace instruments lost in Hurricane Katrina. U2 have also started work on new material with producer Rick Rubin, their site said.

'Raise awareness'

Their next album will be the follow-up to How To Dismantle An Atomic Bomb, which won five Grammy Awards earlier this year - where Green Day picked up record of the year.

The bands would get together "in the coming weeks", Green Day said.

"New Orleans has always been a special city to us, being a hotbed of music and creativity, and it's hard to believe parts of the Gulf region still remain devastated," they said.