His present deal expires in the summer and, having only recently returned from a long-term cruciate injury, he will need to accept a drop in wages.
Blades boss Kevin Blackwell told the club’s official website:"Gary is a very accomplished and a very good defender - that is why Scotland still want him even after his long absence,"
"I hope we can do a deal. There will have to be a big compromise, not least on his part, because he has been out for 18 months. But he is a sensible lad so there is a chance."