The club's chief executive, Martin Edwards, and their manager Alex Ferguson put on a united front with David Davies, the FA's interim executive director, as they tried to justify the unpopular decision.
In the background the recurring theme was of England's 2006 World Cup bid and the guidance from the Government which persuaded United to ditch the game's oldest domestic tournament for its newest global prize because of fixture congestion.
United say they were left with little choice when the FA told them of the possible risks to England's hopes of staging the World Cup if they did not take part in Fifa's new tournament, the World Club Championship in Brazil next January.
"We had to think of the situation regarding England hosting the World Cup," Ferguson said. "No one wants to see them not get it. I dare not think of the criticism we would have received if we had refused. That was unthinkable - and that's a Scotsman talking."
Edwards echoed those sentiments. "If we had not entered this tournament, England's opportunity to host the 2006 World Cup would have been in jeopardy," he said. "It might even be stronger than that. We've given England an opportunity now. You cannot expect our players to play 70 games. Something had to give. We are disappointed for our supporters. The League couldn't give and neither could the European Cup. For one year the FA Cup has to give."
Davies had been in talks at Old Trafford for three hours before the announcement. He tried hard to explain that the risk of devaluing the FA Cup was a worthwhile gamble but admitted that the World Club Championship, the cause of the problem, was a competition that had initially been an unwanted prize.
"We opposed it initially, but we've had to look outwards," Davies said. "Whether we like it or not there is going to be a World Club Cup in the future. England has a choice, either it wants to be part of that or it doesn't. We have to be leaders on the world stage."
However, United's sacrifice may not be enough to convince Fifa that England is the ideal venue for 2006.
"We can't say we are favourites, but we've had reason in the past 12 months to believe that England's is the bid to beat now," Davies said. "England is the best venue with the best stadia and football environment. England is running an outstanding campaign and that is perceived around the world."
Lee Hodgkiss, a spokesman for the Independent Manchester United Supporters Association, said: "My reaction is one of total disappointment. I blame the Government and the FA. I think it is tragic that they are about to sell the jewels of English football down the pan in the slim hope of us getting the World Cup. They [United] were damned if they did and damned if they didn't.
"Going means that fans are deprived of their team taking part in the oldest, most traditional domestic trophy in the world.I feel sorry for the team that wins the FA Cup next season. What a hollow victory it will be knowing the greatest team in Europe weren't taking part."
AXA, the FA Cup sponsors who only started its backing of the tournament last year, said it will seek talks "sooner rather than later" with English football's governing body over the decision of the cup holders to pull out.
United lifted the trophy in May when they completed the double with a 2-0 win over Newcastle United at Wembley.Reuse content