Sepp Blatter has reminded clubs that it is 'mandatory' for them to release players aged 23 and under for this summer's Olympic Games.
The Fifa president has written to all 205 member associations in an attempt to quell the growing discontent from a number of sides at the loss of key players for the tournament in China.
Werder Bremen and Schalke have threatened to take the issue to the Court of Arbitration for Sport after seeing Brazilian duo Diego and Rafinha called up by their country.
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.
He continued: "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 are set to lose Javier Mascherano to the Argentina Olympic squad, despite the fact he is 24.
Manchester City's new Brazilian striker Jo, who is 21, has been selected and while manager Mark Hughes would prefer to have his £19million signing available, the club have made no attempt to prevent him going.
Hughes told the club's official website: "We're a little bit frustrated by the fact that he's gone to the Olympics, ideally we'd have preferred him to stay with us, but we have to respect that. It's a high-profile competition and we look on it as something positive.
"The type of players Brazil are taking with them show that it's viewed in a great light in their country.
"He's part of a very select few players who've been given the opportunity to win the Olympics for Brazil, which they have never done, so I think he'll benefit from the experience."

Beckham - Henry isn't a cheat
Bolton 0-2 Blackburn - Megson
Bolton 0-2 Blackburn - McDonald
Bolton 0-2 Blackburn - Nelson and Dunn
We're not proud - Malouda
The Sky Bet Show - Sunday
Galaxy gold for Becks
Hull 3-3 West Ham - Zola
| Time | Fixture |
|---|---|
| Sunday 22nd November | |
| Barclays Premier League | |
| 13:30 | Bolton vs Blackburn |
| 15:00 | Tottenham vs Wigan |
| 16:00 | Stoke vs Portsmouth |
| Wednesday 25th November | |
| Barclays Premier League | |
| 19:45 | Hull vs Everton |
| 20:00 | Fulham vs Blackburn |
| Saturday 28th November | |
| Barclays Premier League | |
| 15:00 | Blackburn vs Stoke |
| 15:00 | Fulham vs Bolton |
| 15:00 | Man City vs Hull |
| 15:00 | Portsmouth vs Man Utd |
| 15:00 | West Ham vs Burnley |
| 15:00 | Wigan vs Sunderland |
| 17:30 | Aston Villa vs Tottenham |
| Sunday 29th November | |
| Barclays Premier League | |
| 12:00 | Wolverhampton vs Birmingham |
| 13:30 | Everton vs Liverpool |
| 16:00 | Arsenal vs Chelsea |
| Saturday 5th December | |
| Barclays Premier League | |
| 12:45 | Portsmouth vs Burnley |
| 15:00 | Arsenal vs Stoke |
| 15:00 | Aston Villa vs Hull |
| 15:00 | Blackburn vs Liverpool |
| 15:00 | West Ham vs Man Utd |
| Time | Result |
|---|---|
| Saturday 21st November | |
| Barclays Premier League | |
| Liverpool 2 - 2 Man City | |
| Hull 3 - 3 West Ham | |
| Chelsea 4 - 0 Wolverhampton | |
| Sunderland 1 - 0 Arsenal | |
| Man Utd 3 - 0 Everton | |
| Birmingham 1 - 0 Fulham | |
| Burnley 1 - 1 Aston Villa | |
| Monday 9th November | |
| Barclays Premier League | |
| Liverpool 2 - 2 Birmingham | |
| Sunday 8th November | |
| Barclays Premier League | |
| Hull 2 - 1 Stoke | |
| Wigan 1 - 1 Fulham | |
| Chelsea 1 - 0 Man Utd | |
| West Ham 1 - 2 Everton | |
| Saturday 7th November | |
| Barclays Premier League | |
| Aston Villa 5 - 1 Bolton | |
| Blackburn 3 - 1 Portsmouth | |
| Tottenham 2 - 0 Sunderland | |
| Wolverhampton 1 - 4 Arsenal | |
| Man City 3 - 3 Burnley | |
| Wednesday 4th November | |
| Barclays Premier League | |
| West Ham 2 - 1 Aston Villa | |
| Sunday 1st November | |
| Barclays Premier League | |
| Birmingham 0 - 0 Man City | |
| Saturday 31st October | |
| Barclays Premier League | |
| Arsenal 3 - 0 Tottenham | |
Pictures from Saturday's action where Liverpool draw with Man City and Arsenal lose away.
Take a look back at what Liverpool and Man City fans had to say following a 2-2 draw at Anfield.
Bristol City fan Hannah Shine was strutting her as the Soccerette in the Soccer AM studios this week.
Jermain Defoe helped himself to five goals as Tottenham demolished Wigan 9-1 at White Hart Lane to move into fourth spot in the table.
Follow all the action from Sunday's packed programme with the skysports.com Score Centre.
Bolton squandered the chance to climb out of the bottom three as they were beaten 2-0 at home by Blackburn.
David Dunn has played down speculation that he could be able to force his way into the England squad.
Emmanuel Adebayor feels Man City need to learn how to kill games off if they are to break into the top four.