A Fifa-appointed judge has confirmed clubs are obliged to release players aged 23 and under for next month's Olympics football tournament in Beijing.

A statement issued by world football's governing body Fifa today confirmed the judge of the Players' Status Committee, Slim Aloulou, agreed with Fifa's previous ruling that it was "mandatory" for players to be released for Olympic duty.

The judge was called to rule on the matter after Werder Bremen, Schalke and Barcelona questioned the stance as the Olympics do not appear on Fifa's official calendar.

Bremen and Schalke are unhappy with the inclusions of Diego and Rafinha, respectively, in the Brazil squad, while Barca are trying to prevent star forward Lionel Messi joining up with Argentina.

The Court of Arbitration for Sport will now have the final say on the matter after Bremen and Schalke filed complaints, with Barca having indicated they will do likewise.

A statement issued by Fifa read: "The single judge of the Players' Status Committee, Slim Aloulou (Tunisia), decided today … that the release of players under the age of 23 for the Men's Olympic Football Tournament Beijing 2008 is mandatory for all clubs. Previously, on July 29th, 2008, the Fifa emergency committee also took a decision in the same sense.

"The decision of the single judge was taken after Fifa had received requests from the German football association on behalf of its affiliate club FC Schalke 04, as well as from SV Werder Bremen, and Spanish club FC Barcelona directly, in connection with the release of their players under the age of 23 for the Men's Olympic Football Tournament.

"The single judge - while referring to the situation of the players belonging to the clubs in question - deemed that he should address the question of the release of all players under the age of 23 for that competition.

"The single judge determined that the international match calendar is not of relevance in establishing whether clubs are obliged to release players for the Men's Olympic Football Tournament."