Sir Alex Ferguson has accused England coach Sven-Goran Eriksson of having a 'half-baked idea' about Wayne Rooney's battle to be fit for the World Cup finals.
The United boss fears the forward, who is recovering from a broken metatarsal in his right foot, may be 'pressured into playing before he is ready' and has called for a 'realistic approach' from the England camp.
Eriksson has hinted he will name Rooney in his provisional England World Cup squad tomorrow and hopes he will recover in time to play some part in Germany.
But Manchester United boss Ferguson fears Rooney could aggravate the injury by attempting a comeback too soon.
'I don't want any complications with Wayne's broken foot - especially with a bandwagon gathering pace to get him to the World Cup come hell or high water,' Ferguson told the News of the World.
'Let's get it straight right now. For the sake of the boy himself and the rest of the England team, we at United will do everything possible to get him fit in time.
'But I am not going along with this half-baked idea of him going to Germany 80% fit and then find him being pressured into playing before he is ready.
'That was the experience of David Beckham in the last World Cup, and it was a disaster - because he wasn't right. I know Wayne is a special player. But he would up against highly-honed opponents - and in those circumstances, you not only need to be physically fit but match fit too.
'Wayne is young, and in the environment of a World Cup, it would be easy to persuade him to play despite not being fully fit. What is needed here is a realistic approach.'
Rooney suffered the injury in a tackle by Paulo Ferreira during Chelsea's title-clinching 3-0 victory at Stamford Bridge.