The Reds' fourth-round trip to Eastleigh or Newport County will be played on Sunday 28 January, kicking off at 16:30 GMT.
This is due to the intriguing clash being selected for live TV coverage on BBC One, BBC iPlayer and BBC Sport.
Whoever earns the right to face United will set up a first-ever meeting with our club in any competition.
Our two prospective opponents play each other again next Tuesday, 16 January, in a replay at Eastleigh after the National League side forced a draw in the initial encounter at Newport's Rodney Parade ground.
James Clarke gave the League Two side the lead just before the hour mark but their visitors from Hampshire equalised dramatically through Chris Maguire eight minutes from time.