The Red Devils are expected to be active in the upcoming market despite the financial impact of the coronavirus outbreak, which is likely to be felt across the world of football.
The speculation surrounding Sancho's future has gathered pace in recent days with the England international being left out of BVB's starting XI since the team's return to Bundesliga action in the middle of May.
Grealish and Dembele have also been linked with moves away from Villa and Lyon respectively this summer, while Werner's future also remains the subject of much speculation.
Liverpool have been strongly linked with the Leipzig striker, but it has been suggested that the coronavirus pandemic could see the proposed deal fall through ahead of the 2020-21 campaign.
United signed Odion Ighalo on loan from Shanghai Shenhua in January but have still not officially replaced Romelu Lukaku, who left Old Trafford for Inter Milan last summer.