Fans twice broke into the ground and got onto the pitch, while violent clashes outside between the 1,000-strong demonstration and police left two officers injured.
United and the security company they employ, Controlled Group Solutions, face questions over their handling of the situation considering up to 10,000 demonstrators were expected.
Manchester United will review security at Old Trafford after hundreds of protesting fans were able to get inside the stadium and onto the pitch on Sunday
Questions will be asked of the security arrangements as the stadium was stormed by fans
Fans were able to get onto the playing surface unchallenged after gaining access through two separate entrances close to the Munich Tunnel.
Greater Manchester Police also seemed unprepared for the escalation after bringing in officers from neighbouring forces to quell the violence.
United declined to comment on whether a review will take place, but it’s understood the club will look into what happened and how it got out of hand.
Club sources say it was the intention to be non-confrontational, in keeping with a peaceful protest, and that installing barricades and more heavily armoured police from the start would only have risked inflaming the situation.
Tensions escalated when police moved in to move the protestors away from Old Trafford
Bottles and other projectiles were hurled at the riot officers from the protesting fans
Hundreds of Manchester United fans have stormed the pitch at Old Trafford in protest at the club’s American owners ahead of Sunday afternoon’s match with Liverpool
They are keeping the finger of blame firmly pointed at the minority of troublemakers who caused a Premier League fixture to be postponed due to a protest for the first time.
A United statement read: ‘Following discussion between the police, the Premier League, Trafford Council and the clubs, our match against Liverpool has been postponed due to safety and security considerations around the protest.
‘Discussions will now take place with the Premier League on a revised date for the fixture.
The crowd that breached Old Trafford perimeter gathered in front of the south stand, lighting smoke flares and chanting
The Glazer family, United’s owners, signed the club up to the European Super League before making a u-turn 48 hours later amid a furious backlash
‘Our fans are passionate about Manchester United, and we completely acknowledge the right to free expression and peaceful protest.
‘However, we regret the disruption to the team and actions which put other fans, staff, and the police in danger. We thank the police for their support and will assist them in any subsequent investigations.’