Welbeck is currently earning around £15,000-a-week at Old Trafford, but the new deal would see him earn around £45,000-a-week.
The England striker is keen on staying at Old Trafford after moving ahead of Dimitar Berbatov in the pecking order.
Welbeck still has 18 months left to run on his current contract with United.
Welbeck impressed while on loan at Sunderland last season and has been outstanding since returning to Old Trafford.
