Blatter has sent a letter to all member associations saying the release of players aged 23 or under is mandatory for the Olympics.

His move comes after two German clubs, Werder Bremen and Schalke, both filed complaints after their Brazilians Diego, 23, and Rafinha, 22, chose to join up with their country's Olympic squad in defiance of the clubs' wishes.

But Blatter said in his letter: "The release of players below the age of 23 has always been mandatory for all clubs. The same principle shall apply for Beijing 2008."

The fact that this tournament is not included in the co-ordinated international match calendar "does not mean that there is no release obligation for the relevant clubs," he added.

"It would appear to be against the spirit of the Olympic regulations to hinder players under the age of 23, who are actually the core of the squads participating in the Men's Olympic Football Tournament, to take part in the final phase of the event."

Blatter confirmed that it was not compulsory to release players over the age of 23 - three are allowed per squad - but appealed for goodwill from clubs.

Liverpool will lose Javier Mascherano to the Argentina Olympic squad for example despite the fact he is 24.

Manchester United's 20-year-old Brazilian Anderson is also going to Beijing but the club have made no attempt to stop him doing so.

All clubs however will watch closely to see the outcome of Werder Bremen's insistence they will go to the Court of Arbitration for Sport in a bid to end the row with playmaker Diego.

The German club is arguing that as the tournament is not part of the international calendar there is no obligation to release the players.