The Voice coaches will collaborate for Aguilera's seventh studio album, which is due out later this year.
"It's a song for her album. I won't disclose the title, because it could possibly be a working title," Green told Billboard.
"We've talked about it amongst ourselves, and I'm gonna go in on it and work it out. It'll be the second song we've done."
Speaking recently about her new material, Aguilera explained: "My album is going to be amazing. I'm just thrilled. I've been in the studio hard at work.
"The different producers I'm working with have excited me so much and have given me amazing tracks and beats and material that I can write to."
The singer has also insisted that her new collection of material is about "quality over quantity".
Watch the music video for Christina Aguilera's 'Fighter' below: