• this follows a discussion between the Police, the Premier League, Trafford Council, and the clubs.
• United fans got on to the pitch to protest and after they were removed, some got back on to it later on.
Manchester United has released a statement confirming the game has been postponed.
"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 today," said United.
"Discussions will now take place with the Premier League on a revised date for the fixture."
The game was set to kick off at 16:30 BST but was put back on safety grounds.
United fans got on to the pitch to protest and after they were removed, some got back on to it later on.
Both clubs have submitted their team line-ups for the fixture but neither are yet at the ground.
The Premier League said on its live blog: "After the security breach at Old Trafford, we can confirm the Manchester United v Liverpool match will not kick off at 16:30 BST.
"The safety of everyone at Old Trafford is paramount.
"At present, there is no revised kick-off time. We will update accordingly."
All fans are believed to have been ejected from the ground and a sweep of the stadium is going to take place.