There are other innovations in the tournament, including a rule whereby players can start dribbling from free-kicks, instead of passing them, while kick-ins and dribble-ins replace throw-ins.
Any player receiving a yellow card is sidelined for five minutes, while anyone sent off for two bookings can be replaced by a substitute after 10 minutes. No replacement is permitted for a straight red card.
A penalty shootout will be used to determine placings if teams are level on both points and goal difference in the group stages.
United are in Group B, alongside Jeonbuk Hyundai Motors (South Korea), FC Copenhagen (Denmark) and PSV Eindhoven (Netherlands).