The Whites under-23s will face City's under-23s in their final home league game of the season next Friday night and Leeds are hoping to rival the current record attendance for a Premier League Two game.
Everton currently hold that record with a gate of 16,935 and Leeds had already sold 10,000 tickets for the City clash by Wednesday afternoon.
Tickets are priced at £6 for adults or £3 for concessions and are available at the club website HEREUnited's under-23s currently sit fourth-bottom in Premier League Two Division One with three games left.
Andy Taylor's young side are four points clear of the drop zone but have played one game more than second -bottom Chelsea.
United's under-23s will take in their third last game of the season away at ninth-placed Brighton on Friday afternoon (kick-off 2pm).