The 20-year-old striker has had an outstanding first season on loan at Sunderland, and was rewarded last Tuesday with an England debut against Ghana.
Bruce sees him as a likely international star of the future, and told BBC Radio 5 Live's Sportsweek programme: "I would love to buy him, but I don't think that might be possible with the talent the kid's got. It isn't often Manchester United let one of their bright young players go.''
That will not stop Bruce trying, but he is realistic about his prospects of success.
"We'll have a conversation in the summer,'' he said. "But if I was a betting man, I think Sir Alex would be holding on to him - and maybe we could have him for another season if possible.''
Either way, Bruce has no doubt Welbeck will come of age for his country.
"He has flourished since he has been with us because of one thing - he has played,'' the Black Cats boss added. "I don't think in two or three years (at United) he has played more than six games on the spin.
"Danny Welbeck is a fantastic young talent. He's had a fantastic season with us, for such a young boy. So why not (play him for England)? If they've got the talent, like (Jack) Wilshere, it bodes well.''