CELTIC have made an official approach to Dundee United for midfielder Stuart Armstrong.
Discussions regarding a fee are ongoing for the 22-year-old, who has 18 months remaining on his contract at Tannadice.
United have slapped a £2.5million price tag on the player’s head.
The Hoops have already secured the services of Armstrong’s team-mate Gary Mackay-Steven, who will join up in the summer after signing a pre-contract agreement last week.
Armstrong, who joined the Tayside outfit from Inverness Caley Thistle in the summer of 2009, hit the winner when United shocked the SPFL champions 2-1 at Tannadice earlier this season.
Ronny Deila has already likened him to Germany’s World Cup-winning midfield superstar Thomas Muller.
Armstrong scored this winner against Celtic in December when the teams met in the league match at Tannadice where Celtic had a goal controversially disallowed due to an incorrect offside call.