The 17-year old defender has been attracting the attentions of a number of clubs but the Black Cats have been the first to lodge an official bid according to Terrors boss Jackie McNamara.
"The latest is that he is still a Dundee United player," he said.
"The club accepted another bid from Sunderland and he went down to see the facilities.
"I think it is important now that we have that dialogue with John. If [joining Sunderland] is what he chooses to do then we will never stand in anybody's way but, if you are asking my opinion, then I think he would be best to stay here for the next couple of years and get a few games under his belt.
"It will be his decision. He has just turned 17, it is all about his development. He is part of our first-team squad at such a young age and it would be good for him to play 100 or 200 games first and get that experience."
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