The Manchester United winger is keen to stay at Old Trafford but his current contract expires in 2019, and Southampton are reluctant to sell their talisman, according to TalkSport.
Read more: The Premier League club are keen to bring in another winger but they cannot afford to lose McCormack.
Southampton are also struggling to replace the likes of Paul Pogba and Kevin De Bruyne.
United are prepared to sell McCormack for around £15million, but Southampton want more for him.
The 24-year-old has not played a senior match since his move to Southampton in August.
The England international is now on loan at Queens Park Rangers, where he has been helping them to a top-four finish.
A loan deal to the Championship side has also been agreed, with McCormack joining on a two-year deal worth £7.5million.
Read More: McCormack’s move to United is a blow for Southampton as they aim to strengthen their squad ahead of the transfer window, which opens on Saturday.