BIRMINGHAM 1 (Elliott 36), LEEDS 2 (McCormack 70, Diouf 75 pen)
Birmingham: Doyle, Caldwell, Davies, Burke, Robinson, Morrison (Lovenkrands 76), Gomis, Elliott, Redmond (Zigic 82), Caddis, King. Subs: Townsend, Ibanez, Hancox, Hales, Higgins.
Leeds: Ashdown, Byram, Peltier, Lees, Drury (White 10), Green, Austin, Brown, Varney, Diouf (Pearce 90), McCormack. Subs: Kenny, Tate, Norris, Hall, Somma.
Referee: A Woolmer
Booked: Gomis, Elliott (Birmingham) Brown, Ashdown (Leeds)
Att: 8,926 (1,547 Leeds)
United manager Neil Warnock named a much changed team from the defeat at Barnsley on Saturday for Tuesday evening's FA Cup 3rd round replay against Birmingham City at St. Andrews..
Goalkeeper Jamie Ashdown replaced Paddy Kenny, Adam Drury made his return to the starting line-up after illness, defender Tom Lees, along with midfield duo Michael Brown and Luke Varney were recalled and there was also a start for striker Ross McCormack in place of the latest sickness bug victim Luciano Becchio.
There was a great turn out from the travelling fans on a freezing cold night and they were warmed by a positive start by United. Rudy Austin had a couple of wayward attempts as Leeds enjoyed some good possession.
The boss was forced into making an early change, though, when the injured Adam Drury was replaced by Aidy White. White's first contribution was to deliver a good cross which Varney headed towards goal.
Birmingham carved out their first chance on 15 minutes when Wade Elliott sent a shot wide after good work from Marlon King.
Both sides showed plenty of early endeavour but both defences were on top and chances were scant during the opening half hour.
The home side had to scramble to clear their lines after a Leeds raid following the first United corner of the game, but Birmingham swiftly hit back, testing Jamie Ashdown for the first time.
And they went in front on 36 minutes then Nathan Redmond created a chance for Elliott who converted from close range.
United almost hit back straight away, but Varney's header went wide of the mark, Ross McCormack also sent a free kick wide in the minutes leading up to half time.
United started the second half in positive fashion, putting Birmingham under some early pressure. Colin Doyle had to get down well to deny Austiin.
Leeds looked sharper than in the first half and the passing and movement caused the home side problems. Paul Green and El-Hadji Diouf both found space well, and Varney continued to work his socks off in search of an opening.
Neil Warnock's side continued to push forward and Birmingham had to again clear their lines after a United corner.
United's pressure on the Birmingham goal paid off on 70 minutes when a cross was laid back by Diouf into the path of McCormack who drilled the ball past Doyle to level the score.
Leeds continued to advance on the Birmingham goal with Paul Green forcing a good save from Doyle after a great cross from Varney.
In the 74th minute United were awarded a penalty when Paul Robinson handled an attempted cross. Diouf stepped up to take the spot kick and coolly slotted it home to put Leeds within touching distance of a fourth round tie with Tottenham.
Still United came forward and after another penalty appeal was waved away, Green hooked a shot over the top.
With five minutes remaining Birmingham substitute Nikola Zigic had a header blocked on the line, and Peter Lovenkrands brought a great save out of Ashdown.
Three minutes of time were added on but it was United and the magnificent 1,547 travelling fans who were celebrating a place in the fourth round of the competition.