Dundee United manager Jackie McNamara has warned Celtic that they will have to offer "silly money" in order to land midfielder Stuart Armstrong in January.

The 22-year-old, who scored the winning goal against the Hoops in yesterday's meeting between the two clubs, is said to be one of Ronny Deila's top New Year transfer targets.

However, McNamara insists that it will take a serious offer from the Scottish Premiership leaders if they are to part company with Armstrong

"We would want the going rate," he is quoted as saying by the Daily Mail. "We don't need to sell, we're debt free, everything is good. If the right offer came in, I'm sure the chairman and the rest of the board would look at it.

"But the most important thing is to keep them here, let them progress and learn. We would like to have done that with Andrew [Robertson] and Ryan [Gauld] in the summer — but there comes a point when it is too good to turn down, not just for the club but for the kids themselves. Of course, silly money changes everything.

"Speculation has been part of it since I came here. And it will be until the end of January when the window closes. I'm hopeful I will still have the same squad, maybe one or two players coming in, instead of going out."

Armstrong has appeared 17 times for Dundee this season, scoring three goals.