The two pop stars have enjoyed a friendly rivalry in recent weeks but that all changed when George accused the One Direction pin-up of going too far.
He tells New York's Radio 955, "I'm not sure what his (Malik) problem is to be honest. It started off that I thought we were just having a bit of banter, but he seemed to get a bit serious.
"I tried to palm it off as being friendly again, but you can only take so many insults and eventually I just said, 'Alright listen - if you've got a problem, come and see me in New York when we're there doing a gig together and we'll sort it out'."
The showdown could come at the city's Jingle Ball later this month (Dec12).