It is expected that if the player leaves in the January transfer window that the Tannadice club are expected to receive around £400,000 from the deal.
The 20-year-old, whose contract runs out in the summer, has attracted the attention of clubs on both sides of the border despite making only seven first team appearances for the Tayside outfit.
The Scotland Under-21 international was offered a contract extension by the Tannadice club in September, but he turned it down with the likes of Rangers, Newcastle United and Celtic keeping a keen eye on the youngster.
After West Brom lodged their bid, which was accepted, Rangers manager Ally McCoist was quick to highlight his interest in signing the player.
According to the official Rangers website, McCoist has revealed that the club have made contact with United to register their interest in the player.
McCoist said: “We’ve spoken to Dundee United to let them know our intentions and now we need to speak to young Scott and his representatives. He is still United’s player but I would have to say he is a very, very good one and in terms of young talent in the country, he’s up there with anybody.
“Time will tell (if Rangers can compete financially for Allan’s signature) but that’s where we are. Teams at the bottom end of the Premiership and in the Championship are more than capable of outbidding us and offering higher wages.
“That’s just a fact of life but I think we would perhaps be in a position to go to Dundee United and see what we can offer them. Again, time will tell on that one.”
Allan is a product of the Dundee United youth system and spent some time on loan at Forfar Athletic.