LONDON: FIFA president Sepp Blatter said on Wednesday that clubs must release their eligible under-23 players for the Olympic soccer tournament despite the claims of Europe's leading clubs that they were under no obligation to do so.

FIFA, world soccer's governing body, and the European Club Association (ECA), the successor to the G14, which represents Europe's leading clubs, issued contradictory statements on Wednesday with FIFA reaffirming it was mandatory for clubs to release their players.

Blatter, in a letter to all FIFA members said: "The release of players below the age of 23 has always been mandatory for all clubs. The same principle applies for Beijing 2008."

He added that the fact that the Beijing Olympics was not included in the coordinated international match calendar did not mean there was no release obligation for the relevant clubs."

However, ECA chairman Karl-Heinz Rummenigge said in a statement that there "was no legal obligation" on clubs to release their players for next month's Olympic tournament.

Rummenigge said: "As the Olympics is not included in the harmonized International Match Calendar, the obligation to release players for national team matches according to the FIFA Regulations on the Status and Transfer of Players does not apply.

"We, therefore, support all clubs that currently face losing important players."

Earlier this week, Brazil defender Rafinha absented himself without leave from training with Schalke 04 in Germany after it repeatedly refused to release him for the Games.

On Tuesday, Werder Bremen playmaker Diego defied orders from his club and left Germany to join the Brazil squad, while the Brazilian FA (CBF) criticized Real Madrid's decision to pull Robinho out of the squad on Wednesday saying the timing of the Spanish club's decision had disrupted their preparations.

Schalke 04 said on Wednesday it would take its dispute with Rafinha to the Court of Arbitration for Sport, following Werder Bremen's decision to do the same on Tuesday.

Schalke said it was taking the step after it received no response by noon on Tuesday to letters of protest to the International Olympic Committee (IOC) and the Brazil federation (CBF) sent a day earlier.

The disagreement over the status of the Olympic tournament centers on the fact that the Games is not included in the international match calendar.

FIFA says that the omission is an irrelevance and the Olympic tournament is deliberately not included in the international calendar.

In his letter Blatter added: "Due to its unique character the men's Olympic football tournament has always been intentionally treated differently. However this does not mean that there is no release obligation for the relevant clubs."

The ECA takes a different view and said in its statement: "The ECA suggests that FIFA president Sepp Blatter should define clear guidelines and regulations in consultation with the IOC regarding subsequent Olympic Games, once the current framework for the Olympic football tournament expires.

"ECA would be happy to contribute to the development of these future guidelines on behalf of the clubs."

Schalke sporting director Andreas Mueller said on Wednesday: "Even if Mr Blatter is president of FIFA, his remarks are still purely arbitrary. It doesn't change our view. We'll wait for the CAS ruling. FIFA is forcing clubs and players into breach of contract."

Werder Bremen sporting director Klaus Allofs agreed, saying: "As in previous letters from FIFA, president Blatter bases his comments in principle on custom and practice, and the special charter of the Olympic tournament. But in the view of our federations, the DFB and the DFL, this letter has no binding character whatsoever."

Olympic squads can also include up to three players aged over 23 in their squads, but their inclusion is not mandatory.