The Newcastle youngster spent the second half of the season on-loan in Paisley but is now out of contract.
He and best friend Paul Dummett - who was loaned to the Buddies for the entire season - have both been offered one-year extensions by United boss Alan Pardew.
However, terms have yet to be agreed and reports have suggested Clydesdale Bank Premier League champions Celtic could swoop for the pair.
Newton made just his second appearance for Danny Lennon's team when he helped stun the Hoops with a 3-2 win in the semi-finals of the League Cup and netted the decisive strike as Saints then beat Hearts by the same score in the final.
However, he told Press Association Sport: "A move to Celtic would interest anyone, wouldn't it? I would definitely consider it but I don't think there is any real substance to it. It just seems to be paper talk."
- Sports & Recreation
- Paul Dummett
- Clydesdale Bank Premier League
- Danny Lennon