The two stars have just released the track 'Rain On Me', which is the official second single from Gaga's upcoming album 'Chromatica', and Charli, 27, took to Twitter to praise Gaga and Ariana.
She wrote: ''really feeling a lot of the melodies in this new gaga x ariana (sic).''
Meanwhile, Gaga, 34, recently revealed she and Ariana, 26 - who has battled with a number of tragedies in her life in the past few years, including the bombing at her 2017 Manchester Arena gig and the death of her ex Mac Miller - bonded while working on the song.
Gaga explained: ''That woman has been through some really tough, really hard life testing stuff, undoubtedly. And her ability to move on...'
''To be with her and hold her and be like, 'Anything that you feel chains you, any pop cultural construct that you feel you have to live up to, I'd like you to please forget about it and be yourself.'''
However, Gaga admitted it took her some time to open up to friendship with Ariana, because of her own mental health struggles.
She said: ''When she came into the studio, I was still crying and she was not. And she was like, 'You're going to be OK. Call me; here's my number'.
''And she was so persistent. She would try over and over again to be friends with me. And I was too ashamed to hang out with her because I didn't want to project all of this negativity onto something that was healing and so beautiful. And eventually she called me on my sh*t. She was, 'You're hiding'. And I was ... and then this friendship blossomed.''
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