The 19-year-old has starring for the Rangers B team since joining from Manchester United in deal reported to be worth £750,000 last summer.
However, Republic Under-21 boss Jim Crawford confirmed that the Ibrox youngster has opted to switch eligibility to their Northern neighbours.
"I spoke to Charlie a few weeks ago," Crawford told the League of Ireland Central Podcast.
"It's unfortunate that he's looking now to go and play with Northern Ireland.
"This was the danger of the 2002 group that haven't been involved in international football for so long [because of the pandemic].
"I had to say to Charlie that you have to realise that we have Gavin Kilkenny, Conor Coventry, Ross Tierney, Dawson Devoy, Will Smallbone, these players that are all really talented players. Charlie is a very good player as well but unfortunately he didn't get ahead of them."