It has been reported that Premier League giants United have scouted the 15-year-old, who is a box-to-box midfielder.
The report has claimed that Chelsea, Arsenal, Tottenham and Leicester City are also keeping tabs on the teenager.
Celtic want to keep hold of the highly rated and hugely promising youngster, and have offered him terms on his first pre-professional contract amid interest from clubs in England, according to the report.
Celtic are a massive club and have a very good youth academy, and it would make sense for Kelly to stay at the Hoops for now.
True, the likes of Tottenham, United and Chelsea are global brands and are hugely attractive, but the midfielder is only 15 years of age and is still growing as a footballer.
At such a young age, it is important to learn the game, enjoy oneself and work hard.
Staying at Celtic would help him grow and develop at his own pace, and he would not be under as much pressure as he would be if he was to move to a club in England this summer.