The Poland international has been heavily linked with a move to United in recent weeks, having netted 30 goals last season helping Borussia Dortmund to win a domestic double.
Franciszek Smuda is adament that Lewandowski will be a United player next season and also claims that Lukasz Piszczek and Jakub Blaszczykowski will also depart from Dortmund this summer.
"In my opinion, in a moment they will be gone from Borussia," Smuda stated, speaking before the Euro 2012 opener against Greece tonight.
"Lewy' is going to Manchester United, Kuba also somewhere in England, Piszczek to Real Madrid. They have a goal and they want to grow. I base the squad on them."
If Lewandowski does seal a move to Manchester, he'll become the second Dortmund player to move to United this summer.