They led for 86 minutes but just as they were about to reach the fifth round the door was slammed aggressively in their faces. Disappointment, disbelief and pain was ingrained in every movement of the Liverpool players as they dragged themselves from the field and out of the competition.
A replay was the least the visitors deserved for their dogged defending and prodigious labour but, after Michael Owen put them ahead after 155 seconds, United scored twice in the final two minutes through Dwight Yorke and Ole Gunnar Solskjaer. The sting in the tail of this vibrant tie was deadly.
"The game was five minutes too long for us," Gerard Houllier, the Liverpool manager, moaned. "It's a shame because the players could have written a page in the club's history in capital letters. I feel very proud of what we did. I told the players there was nothing to be ashamed of, they could be satisfied with what they did."
It was 1921 the last time Liverpool beat their bitterest rivals in the Cup and Old Trafford fizzed with anticipation as they attempted to put that right. Football enmity paves every foot of the 30 miles that divides Manchester and Merseyside and the heightened passions that a meeting of these teams evokes was apparent from the start.
Tackles flew in as players tried to leave a reminder for the rest of the game but it was the visitors whose left the first significant mark. Jamie Redknapp swept the ball to the right where Vegard Heggem teased Denis Irwin and then arced a perfect cross towards the penalty spot. Owen, inexplicably unmarked, was waiting and with a huge leap and twist he flicked the ball with his head into the bottom corner.
"It was a terrible start," Alex Ferguson, the United manager said. "God almighty, you wouldn't think a 5ft 6in striker would score with a header in the first minutes at Old Trafford. I wasn't too pleased with that."
Liverpool were delighted. They had their goal and could yield ground to the opposition as they protected what they had, striking out from their fortress when the chance occurred. Their defence has been pilloried regularly but yesterday their central core of Jamie Carragher, Dominic Matteo and Steve Harkness put barely a foot wrong. Indeed, until the climax, United were reduced to half chances and hit and hopes.
The first arrived when David Beckham's cross from the right seemed too long but Roy Keane stretched and headed with such venom that the ball hit the post and ricocheted to Paul Ince on the line. Somehow it did not go into the net. Henning Berg was also close with a header but Liverpool had weapons of their own and in the closing minutes of the first half only the sharpness of Peter Schmeichel's reflexes denied Patrik Berger.
United had been reduced to near impotence by Liverpool's hard work before the interval but they shook off their sluggishness and began pounding at the door. Ryan Giggs somehow failed to get a touch to Beckham's cross, Keane's shot rebounded off a defender and passed agonisingly close to a post and Matteo crashed an interception towards his own goal and was fortunate to find the one place James was standing.
The impression was building that United were not going to score no matter what they did and that was reinforced after 79 minutes when Keane's shot beat James, hit the post and bounced to safety. Liverpool twice had opportunities to kill off the tie themselves but first Robbie Fowler fired wide after Owen had ripped apart United's left flank, then Jaap Stam and Peter Schmeichel managed to deny Fowler more with luck than with sound judgement.
Those misses proved crucial because, as United contemplated throwing Stam forward as a makeshift centre-forward, they got a goal in the 88th minute. Jamie Redknapp was harshly adjudged to have fouled Ronny Johnsen and Beckham's free-kick was headed down by Andy Cole and tapped over the line by Yorke. Cue home relief so profound you could almost touch it but more was to follow. Deep into injury time Paul Scholes got possession in the Liverpool area and and seemed to have lost the opportunity as he waited an age for the ball to drop for a shot. Instead it fell to Solskjaer, who rifled it past James.
"I've watched Solskjaer's goal on television and he meant to do what he did," Ferguson said. "He looked at the far post, the goalkeeper bought it and he beat him at the near. It was a superb finish." It was a tragic one for Liverpool. "We're not really interested in the FA Cup," Ferguson said with heavy irony. "We showed that today."
Goals: Owen (2) 0-1, Yorke (88) 1-1; Solskjaer (90) 2-1.
Manchester United (4-4-2): Schmeichel; G Neville, Berg (Johnsen, 80), Stam, Irwin (Solskjaer, 80); Beckham, Butt (Scholes, 68), Keane, Giggs; Yorke, Cole. Substitutes not used: P Neville, Van der Gouw (gk).
Liverpool (3-5-2): James; Carragher, Matteo, Harkness; Heggem, Redknapp, Ince (McAteer, 70), Berger, Bjornebye; Owen, Fowler. Substitutes not used: Kvarme, McManaman, Leonhardsen, Friedel (gk).
Bookings: Manchester United: Butt, Keane, Giggs, Scholes. Liverpool: Matteo, Owen.
Referee: G Poll (Tring).
Man of the match: Carragher.