Manchester United have written to the Football Association to say Stuart Pearce cannot select any of their players as part of the three-man over-age contingent for the British Olympic team apart from Ryan Giggs. This means Pearce cannot call on Rio Ferdinand, Wayne Rooney, Paul Scholes or Jonny Evans for London 2012.

Sir Alex Ferguson, the United manager, has also ensured that Javier Hernández cannot play for Mexico at the Games after he was blocked from being selected, according to the director of national teams. Héctor González Iñarritu said: "Alex Ferguson refused to let him compete in the Olympic Games. Alex Ferguson blocked the participation of Javier Hernández."

But Ferguson said he and Mexico's FA had agreed to the withdrawal, telling United's website: "His form last season was fantastic. He's found the second year more difficult, but a lot of that is down to not having a summer break for three years and playing every summer for his country. Next year he will be fine as we have agreed with the Mexican Football Association that he is going to get the requisite rest that he needs to perform in the Premier League."

According to a 2008 court ruling, clubs have the right to refuse to release players for the competition as it is not on the international calendar, but United are taking that position only on their over-age players. Tom Cleverley, Danny Welbeck, Phil Jones and Chris Smalling could still be part of the Olympic squad if they are not picked for the England Euro 2012 squad.

Ferguson will also allow Giggs to participate. The 38-year-old has never played in a major international tournament and has indicated he would accept an invitation so long as the Football Association of Wales did not oppose him doing so. Sources there have confirmed that although they are politically opposed to a GB team, they would not prevent Giggs taking part.

An FA spokesman refused to confirm whether it had received the letter from United. The club were also not commenting.