Manchester United midfielder Eric Djemba-Djemba scored at the end of extra-time to break Leeds' hearts and dump Peter Reid's side out of the Carling Cup.
Brazilian defender Roque Junior had put the home side ahead four minutes after the interval, powering home a header from Seth Johnson's inswinging corner.
But United upped the tempo and David Bellion raced onto Djemba-Djemba's pass to level matters 12 minutes from normal time.
Diego Forlan tapped home in extra-time to put United ahead, but Roque Junior netted again before Djemba-Djemba's late strike won the tie.
49 mins: Roque Junior scores header from Johnson corner
78 mins: Bellion races through to equalise for Man Utd
99 mins: Forlan taps home from Fletcher cross
114 mins: Roque Junior converts Milner's cross
117 mins: Djemba-Djemba's shot loops over Robinson
After a slow start, the first real chance of the contest arrived after 20 minutes, when Forlan brought a terrific low save from Paul Robinson after an incisive pass from Darren Fletcher.
But it was Leeds who were enjoying most of the possession, and they nearly made it count when Roque Junior had a shot blocked and then blazed over the crossbar when United failed to clear a corner.
A double error from John O'Shea nearly let in Alan Smith, but in truth the game barely deserved a shot let alone a goal in a disappointing first period.
Two minutes after the break Leeds thought they had taken the lead, but Smith was adjudged offside after he tapped home when Roy Carroll had saved Johnson's left-foot strike.
But they were not to be denied for long, and with 49 minutes on the clock Roque Junior rose high to power home Johnson's corner past Carroll.
The goal was the cue for United to up the tempo, and they began to assert themselves in their hunt for an equaliser.
Brazilian Roque Junior scored twice for Leeds at Elland Road
Fletcher wasted a great opportunity by firing woefully wide, then Bellion had a goal disallowed for offside as Leeds found themselves under the cosh.
Bellion then tested Robinson with a stinging low drive before he latched onto Djemba-Djemba's pass and slotted clinically through the legs of the Leeds keeper to level.
United so nearly won it in stoppage time when Roque Junior deflected substitute Chris Eagles' cross goalwards only for Robinson to somehow push the ball away and take the game into extra-time.
For the third time the assistant referee's flag ruled out a goal when, nine minutes into the extra period, Forlan met Nicky Butt's cross with a brilliant header into the top corner, but the Uruguayan was adjudged offside.
Leeds were furious that they did not get a penalty when it appeared substitute Cyril Chapuis was brought down in the area, and just moments later Forlan tapped home Fletcher's cross to put United ahead.
Six minutes from the end Leeds got a lucky break when Roque Junior bundled home James Milner's right-wing cross, but back came United and Djemba-Djemba struck from Quinton Fortune's corner to win it.
Leeds: Robinson, Kelly, Camara, Roque Junior, Harte, Milner, Seth Johnson, Olembe, Sakho, Smith, Bridges. Subs: Carson, Chapuis, Duberry, Lennon, Domi.
Man Utd: Carroll, Phil Neville, Gary Neville, O'Shea, Fortune, Fletcher, Butt, Djemba-Djemba, Richardson, Bellion, Forlan. Subs: Howard, Pugh, Lynch, Eddie Johnson, Eagles.
Referee: P Durkin (Dorset).