Aguero will also be out for a Premier League clash against Bournemouth and an EFL Cup trip to Swansea City.
An FA statement read: 'Off the ball incidents which are not seen at the time by the match officials are referred to a panel of three former elite match officials.
'Each panel member will review the video footage independently of one another to determine whether they consider it a sending-off offence.
'For retrospective action to be taken, and an FA charge to follow, the decision of the panel must be unanimous.'
Guardiola said on Sunday that he hadn't seen the altercation but promised City would plough on regardless.
Aguero pulled out of international duty with Argentina this week because of a calf problem and might have struggled for fitness ahead of the United clash.
It would leave Guardiola with decisions to make before the opening duel with Jose Mourinho. With Kelechi Iheanacho as his only recognised striker, Guardiola may be forced to play Nolito or even Raheem Sterling through the middle.