The draw, conducted at Wembley immediately after United's 2-2 draw with Chelsea at Old Trafford, pitched the eventual winners of the replay against City, who beat Barnsley 5-0 on Saturday.
Millwall and Blackburn also drew earlier in the day and will replay on Wednesday, with the winner to face Wigan, who swept aside Everton 3-0 on Saturday.
The semi-finals will be played at the national stadium over the weekend of April 13 and 14.
Anybody else realised that this means one of the "smaller" three clubs will definitely be playing in Europe next year? Millwall, Blackburn, or Wigan definitely in the cup final and either of their potential opponents will definitely qualify for the Champions League. Wigan in the Europa League... I never thought I'd see the day.- pbush77